Lunar touchdown in diplomatic missions

ESET researchers found two beforehand unknown backdoors – which we named LunarWeb and LunarMail – compromising a European ministry of international affairs (MFA) and its diplomatic missions overseas. We consider that the Lunar toolset has been used since at the least 2020 and, given the similarities between the instruments’ techniques, methods, and procedures (TTPs) and previous actions, we attribute these compromises to the notorious Russia-aligned cyberespionage group Turla, with medium confidence. We not too long ago introduced our insights from this analysis at this yr’s ESET World convention and supply extra particulars about our findings on this blogpost.

Key factors of the blogpost:

• ESET Analysis found two beforehand unknown backdoors – LunarWeb and LunarMail – used within the compromise of a European MFA and its diplomatic missions.
• LunarWeb, deployed on servers, makes use of HTTP(S) for its C&C communications and mimics official requests, whereas LunarMail, deployed on workstations, is continued as an Outlook add-in and makes use of electronic mail messages for its C&C communications.
• Each backdoors make use of the strategy of steganography, hiding instructions in photographs to keep away from detection.
• Each backdoors make the most of a loader that makes use of the DNS area identify for decryption of the payload, share parts of their codebases, and have the bizarre functionality of having the ability to execute Lua scripts.
• The loader can have varied kinds, together with trojanized open-source software program, demonstrating the superior methods utilized by the attackers.

Turla, often known as Snake, has been lively since at the least 2004, probably even relationship again to the late Nineteen Nineties. Believed to be a part of the Russian FSB, Turla primarily targets high-profile entities comparable to governments and diplomatic organizations in Europe, Central Asia, and the Center East. The group is infamous for breaching main organizations, together with the US Division of Protection in 2008 and the Swiss protection firm RUAG in 2014. Over the previous few years, we have documented a giant half of Turla’s arsenal on WeLiveSecurity.

Our present investigation started with the detection of a loader decrypting and operating a payload, from an exterior file, on an unidentified server. This led us to the invention of a beforehand unknown backdoor, which we named LunarWeb. Subsequently, we detected the same chain with LunarWeb deployed at a diplomatic establishment of a European MFA. Notably, the attacker additionally included a second backdoor – which we named LunarMail – that makes use of a special technique for command and management (C&C) communications.

Throughout one other assault, we noticed simultaneous deployments of a series with LunarWeb at three diplomatic establishments of this MFA within the Center East, occurring inside minutes of one another. The attacker in all probability had prior entry to the area controller of the MFA and utilized it for lateral motion to machines of associated establishments in the identical community.

Additional examination uncovered further items of the puzzle, together with elements utilized within the preliminary stage of the compromise and a restricted variety of instructions issued by the attacker. The timestamps within the oldest samples and the variations of the libraries used recommend that this toolset has been operational since at the least 2020, probably earlier. Our technical evaluation focuses on the methods these backdoors make use of, comparable to steganography, and communication strategies.

Victimology

In accordance with ESET telemetry, the compromised machines that we managed to determine belong to a European MFA and are primarily associated to its diplomatic missions within the Center East.

Technical evaluation

Preliminary entry

We don’t know precisely how preliminary entry was gained in any of the compromises. Nevertheless, recovered installation-related elements and attacker exercise recommend potential spearphishing and abuse of misconfigured community and utility monitoring software program Zabbix. Potential Zabbix abuse is recommended by a LunarWeb set up part imitating Zabbix logs, and a recovered backdoor command used to get the Zabbix agent configuration. Moreover, proof of spearphishing features a Phrase doc putting in a LunarMail backdoor by way of a malicious macro.

Beneath, we offer particulars of the installation-related elements and preliminary attacker exercise.

Stage 0 – LunarWeb preliminary server compromise

Whereas we don’t have the total image of the preliminary compromise, we discovered an installation-related part in one of many server compromises – a compiled model of an ASP.NET net web page originating from following supply information:

• <IIS_web_root>aspnet_clientsystem_web.aspx
• <IIS_web_root>aspnet_clientsystem_web.cs

The system_web.aspx filename is a identified IoC of Hafnium, a China-aligned APT identified for exploiting vulnerabilities in Microsoft Alternate Server software program. Nevertheless, we consider that is both a coincidence or a false flag.

When the system_web.aspx web page is requested, it responds with a benign-looking Zabbix agent log. Nevertheless, the web page covertly expects a password in a cookie named SMSKey. If offered, the password (mixed with the salt Microsoft.SCCM.Replace.Supervisor) is used to derive an AES-256 key and IV for decrypting two embedded blobs, that are then dropped to 2 short-term information in a listing excluded from scanning.

Whereas we don’t know the password, the file sizes match additional levels within the compromise chain – the Stage 1 loader and Stage 2 blob – containing the LunarWeb backdoor. Lastly, both the attacker or an unknown part renames and strikes the 2 short-term information to their remaining locations, and units up persistence.

Throughout our investigation, we discovered that the attacker already had community entry, used stolen credentials for lateral motion, and took cautious steps to compromise the server with out elevating suspicion. The attacker’s steps included copying two log information over the community; these information have been intentionally named to imitate Zabbix agent logs. The attacker moved them to the IIS net listing because the system_web web page, and despatched a HEAD request to the web page with a password, which resulted within the creation of two information with .tmp filename extensions. The system_web web page information have been then deleted, and the dropped .tmp information containing Phases 1 and a couple of have been moved to the next areas:

• C:WindowsSystem32en-USwinnet.dll.mui
• C:WindowsSystem32DynamicAuth.bin

Lastly, to take care of entry and execute their code, the attacker arrange a Group Coverage extension within the registry utilizing the Distant Registry service.

Stage 0 – LunarMail preliminary person compromise

In one other compromise, we discovered an older malicious Phrase doc, doubtless from a spearphishing electronic mail. Regardless of being a DOC file, it’s really in DOCX format, which is a ZIP archive that may maintain further content material. This doc has uncommon elements: 32- and 64-bit variations of a Stage 1 loader, and a Stage 2 blob containing the LunarMail backdoor.

They’re put in utilizing a VBA macro, executed on doc opening, that does the next:

1. Calculates a sufferer ID from the pc identify and informs its C&C server by pinging a selected URL with the ID in its subdomain.
2. Creates the listing %USERPROFILEpercentGpg4win and extracts the suitable information from the additional content material within the ZIP/DOCX – Stage 1 loader to gpgol.dll and Stage 2 blob to tempkeys.dat.
3. Units up persistence by way of Outlook add-in registry settings and pings one other URL containing the ID.

We didn’t receive the entire doc, nevertheless it in all probability comprises a lure that’s engaging sufficient, since it will probably’t be accessed in any other case, to persuade the sufferer to allow macros.

The paths and names used mimic Gpg4win’s Outlook add-in, GpgOL. As soon as deployed, the Stage 1 loader seems in Outlook Add-Ins, as proven in Determine 1.

Lunar toolset

Following our evaluation of the installers launched within the earlier part, we look at the loaders and end with evaluation of their payloads – two beforehand unknown backdoors. Determine 2 outlines the elements within the two noticed compromise chains.

Stage 1 – LunarLoader

The execution chain begins with a loader that now we have named LunarLoader. It makes use of RC4, a symmetric key cipher, to decrypt the trail to the Stage 2 blob and reads an encrypted payload from it. To make sure that just one loader occasion is lively, it makes an attempt to open after which create a mailslot with a singular identify, as an alternative of a standard synchronization object comparable to mutex or occasion. It additionally creates a decryption key, derived from the MD5 hash of the pc’s DNS area identify, which it verifies. The payload is then decrypted utilizing AES-256, leading to a PE file. LunarLoader allocates reminiscence for the PE picture and decrypts the identify of an exported perform within the PE file, which is then run in a brand new thread. This perform comprises a reflective loader.

Utilizing the DNS area identify for payload decryption serves as an execution guardrail. The loader accurately executes solely within the focused group, which can hinder evaluation if the area identify just isn’t identified.

LunarLoader can have a standalone kind or be part of trojanized open-source software program. We noticed one case of the latter, with a trojanized AdmPwd, which is part of Home windows Native Administrator Password Resolution (LAPS).

We noticed that LunarLoader makes use of three completely different persistence strategies and several other file paths, as proven in Desk 1.

Desk 1. Variants of LunarLoader

Persistence technique	Loader path(s)	Host course of	Observe
Group coverage extension	C:WindowsSystem32en-USwinnet.dll.mui C:Program FilesLAPSCSEAdmPwd.dll*	svchost.exe -k GPSvcGroup	The AdmPwd dll is a identified official file path of Microsoft LAPS.
System DLL substitute	C:WindowsSystem32tapiperf.dll	wmiprvse.exe	Changing a official Home windows DLL.
Outlook add‑in	%USERPROFILEpercentGpg4wingpgol.dll	outlook.exe	N/A

Stage 2 blob – payload container

The blob utilized in Stage 2 consists of 4 entries – together with two unused strings, the place the worth of 1 is the base64-encoded model of the string freedom or dying or freedom or dying (yeah,we’re alive), as proven in Determine 3, and 32-bit and 64-bit variations of the payload.

Whereas the aim of the freedom or dying string within the given context isn’t explicitly defined, it’s frequent for malware authors to incorporate such strings for quite a lot of potential causes, comparable to monitoring completely different variations of their malware, to function a distraction or false lead for analysts, or just as a type of signature or calling card. In some instances, we discovered strings as an alternative of a 32-bit payload – such because the string shit occurs.

We noticed two completely different backdoors used as payloads. The backdoors appear to make use of the next DLL names within the export listing, with these suspected meanings:

• mswt[e].dll – web transport (LunarWeb)
• msmt[e].dll – mail transport (LunarMail)

The e suffix is used for the 64-bit variations. The noticed file paths for the blob are listed within the IoCs part.

Stage 2 payload #1 – LunarWeb backdoor

LunarWeb, the primary payload we found, is a backdoor that communicates with its C&C server utilizing HTTP(S) and executes instructions it receives. We noticed that LunarWeb was deployed solely on servers, not person workstations.

Throughout its initialization, LunarWeb makes an attempt to find or create its state file, which comprises entries associated to its execution. Then it decrypts strings, largely associated to communication, utilizing RC4 with the static key C1 82 A7 04 21 B6 40 C8 9A C3 79 AD F5 5F 72 86. It additionally collects sufferer identification knowledge and makes use of it to calculate a sufferer ID, which is utilized in communications with the C&C server.

After conducting security checks, the backdoor waits for just a few hours earlier than coming into its communication loop. This delay is skipped on the backdoor’s first run. The safety checks embody a restrict of preliminary contact makes an attempt with the C&C server, assessing the backdoor’s lifespan, and checking C&C server accessibility. If any of the security circumstances fail, LunarWeb self-removes, deleting its information, together with the Stage 1 loader and Stage 2 blob. Nevertheless, the persistence technique for the Stage 1 loader is left, probably leaving detectable traces.

Configuration and state

LunarWeb’s configuration is hardcoded into the binary, doubtless from handbook supply code modifications. The configuration varies between samples, together with the C&C servers, their unreachability threshold, the communication format, and the backdoor lifespan.

The backdoor maintains a 512-byte state construction, up to date throughout execution and saved in a file. This file comprises three state slots, accessed by index 0, 1, or 2 as proven in Determine 4. The primary two slots are modifiable, however unused by this backdoor; solely the third slot is used. State slots are encrypted utilizing RC4 with key 99 53 EA 6A AB 29 44 EF BE 36 12 9E F2 3B 5E C9.

The noticed areas of the state information are listed within the IoCs part.

Data assortment

LunarWeb collects the next details about its host pc:

• distinctive sufferer identification obtained by way of WMI queries:
  • working system model with serial quantity,
  • BIOS model with serial quantity, and
  • area identify.
• additional system data obtained by way of shell instructions:
  • pc and working system data (output of systeminfo.exe),
  • surroundings variables,
  • community adapters,
  • record of operating processes,
  • record of companies, and
  • record of put in safety merchandise.

The data is shipped to the C&C server on first contact.

Communication

After initialization, LunarWeb communicates with its C&C server utilizing HTTP(S), beneath which is a customized binary protocol with encrypted content material.

LunarWeb employs three URLs (containing IP addresses as an alternative of domains) for various functions. One URL is used for first contact, importing details about the host pc as described within the earlier part. The 2 remaining URLs are used for getting instructions, every being on a special server. We refer to those URLs beneath as command URLs.

To cover its C&C communications, LunarWeb impersonates legitimate-looking site visitors, spoofing HTTP headers with real domains and generally used attributes. It could possibly additionally obtain instructions hidden in photographs. Impersonated attributes from every noticed LunarWeb pattern are proven in Desk 2.

Desk 2. Impersonated attributes

Host	Person-Agent	Request-URI / Filename
win8.ipv6.microsoft.com	Mozilla/5.0 (Home windows NT 10.0; Win64; x64; rv:80.0) Gecko/20100101 Firefox/80.0	(Non-impersonating URIs)
i1.c1.eset.com	Host: EES Replace (Home windows; U; 64bit; BPC 9.0.2047.0; OS: 10.0.16299 SP 0.0 NT; TDB 57524; TPCAT 0; CL 1.0.0; x64c; APP ees; ASP 0.0; FW 32.0; PX 1; CD 1; RA 1; UBR 2166; HVCI 0; SHA256 1; WU 3; HWF: DA7506AC-AB57-4C28-BC32-E6D90B48B66F; PLOC en_us; PCODE 111.0.0; PAR 0; ATH -1; DC 0; PLID 375-GTM-VO6; SEAT 62f587f1; RET 5004) [sic]	replace.ver.signed livegrid
<MFA_country_news_site>	Mozilla/5.0 (Home windows NT 10.0; Win64; x64; rv:73.0) Gecko/20100101 Firefox/73.0	(Non-impersonating URIs)
ctldl.windowsupdate.com	Microsoft-CryptoAPI/6.1	/msdownload/replace/v3/static/trustedr/en/authrootstl.cab /msdownload/replace/v3/static/trustedr/en/disallowedcertstl.cab /msupload/replace/v3/static/trustedr/stats
ctldl.windowsupdate.com	Microsoft-CryptoAPI/6.1	/msdownload/replace/v3/static/trustedr/en/authrootstl.cab /msdownload/replace/v3/static/trustedr/stats

Notable examples of impersonation embody Home windows companies (Teredo, Home windows Replace) and updates of ESET merchandise. In instances of ESET impersonation, the attackers copied the Person-Agent (the place they slipped in a Host header) and different headers utilized by updates of our product. Unusually, they spoofed a nonexistent area within the Host header.

Sufferer identification is included in HTTP requests, both in a cookie or a URL question parameter. The primary technique makes use of randomly generated cookies with a 16-byte identifier (probably a marketing campaign ID) and a sufferer ID. The second technique appends the sufferer ID twice to the URL. The suspected marketing campaign ID is current in samples utilizing the second technique however just isn’t used. LunarWeb also can use an HTTP proxy server for C&C communications, if wanted.

Receiving instructions

LunarWeb collects instructions from the C&C server by way of a GET request to the command URL. The request and response format range throughout 5 supported codecs, with a hardcoded worth figuring out which to make use of. Desk 3 offers an outline of those codecs. We noticed utilization of codecs 2, 3, and 4.

Desk 3. Communication codecs for getting instructions

Format	Command request filename instance	Response, extraction, decoding	Response decryption, decompression	Observe
0	N/A	Base64	RSA	Brief instructions solely (RSA-4096 512‑byte restrict).
1	N/A	None	RSA	Brief instructions solely (RSA-4096 512‑byte restrict).
2	replace.ver.signed disallowedcertstl.cab (impersonation particular)	Base64 or none	RSA, AES, zlib	Decoding is skipped in situations the place this format is definitely used.
3	<random_5_alnum>.jpg	JPG	RSA, AES, zlib	The info is inside a JPG remark.
4	<random_5_alnum>.gif	GIF	RSA, AES, zlib	The info is inside GIF knowledge blocks.

Relying on the communication format, the info obtained from the C&C server may want decoding utilizing the base64 algorithm or extraction from a picture. JPGs are scanned for the remark marker FF FE, whereas GIFs are parsed utilizing the giflib library. In each instances, the fascinating knowledge is embedded within the buildings of the picture format and never hidden in particular person pixels of a picture, as in LSB steganography for instance.

Communication codecs 0 and 1, although not noticed, merely decrypt ensuing knowledge utilizing RSA-4096. Codecs 2, 3, and 4 are extra complicated. The ensuing knowledge begins with an encrypted AES seed, decrypted with RSA-4096 and used to derive a session key. This session secret’s then used to decrypt the remainder of the info utilizing AES-256, adopted by zlib decompression.

After decryption and, if wanted, decompression, the obtained knowledge ends in a command bundle. This bundle, possessing a singular ID, is in comparison with the final processed ID, saved within the backdoor’s state. If they’re completely different, the backdoor processes the bundle and updates the final ID. The bundle might maintain a number of instructions. Every command is executed, and its output despatched to the C&C server in a single format, with no steganography, as described within the ensuing Exfiltrating knowledge part.

To carry out cryptographic operations, LunarWeb makes use of a statically linked Mbed TLS library. It has two embedded RSA-4096 keys: one for decrypting incoming knowledge and one for encrypting outgoing knowledge. Each use commonplace parameters and are outlined in our GitHub repository.

Exfiltrating knowledge

First, knowledge is zlib-compressed and encrypted utilizing AES-256, with a session key and IV derived from the info’s measurement, additionally producing a hash-based message authentication code (HMAC).

For AES encryption, a random 32-byte AES seed is generated and encrypted utilizing RSA-4096. The seed is used to derive a session key in a PBKDF-like method, SHA-256 hashing the seed and an IV 8,192 occasions. The identical key derivation occurs when decrypting obtained knowledge. The derivation algorithm and encryption code was copied from an older Mbed TLS pattern program that was faraway from the library in 2021.

Lastly, the encrypted knowledge, together with decryption and integrity metadata, is shipped. If output knowledge exceeds 1.33 MB after compression, it’s break up into a number of elements of random measurement (384–512 KB).

POST requests to the C&C server embody impersonation headers and sufferer identification, and their sending is delayed by a sleep of 34 to 40 seconds. Curiously, every command bundle obtained comprises an output URL, which is the place to ship the consequence. This might be a special URI on the identical C&C server, or a totally completely different server. Within the restricted variety of command packages that we noticed, the output URL was the identical because the command URL.

Instructions

LunarWeb helps frequent backdoor capabilities, together with file and course of operations, and operating shell instructions, together with ones by way of PowerShell. One of many instructions stands out, with the moderately unusual functionality of having the ability to run Lua code.

The total record of supported instructions, with further particulars, is proven in Desk 4.

Desk 4. Overview of LunarWeb instructions

Sort	Command	Particulars
0	Run shell instructions by way of a BAT file and get output	Runs specified shell instructions by way of a short lived BAT file %TEMP%<⁠random_9_alnum_chars>.bat. The output is retrieved by way of a pipe (additionally applies to the following 4 instructions).
1	Run shell instructions and get Unicode output	Runs the shell instructions on the command line by way of cmd.exe /c and /U possibility for Unicode output.
2	Run shell instructions and get output	Runs the shell instructions on the command line by way of cmd.exe /c.
3	Run PowerShell instructions by way of a PS1 file and get output	Runs specified PowerShell instructions by way of a short lived script file %TEMP%<random_12_alnum_chars>.ps1.
4	Run PowerShell instructions and get output	Runs specified PowerShell instructions by way of powershell.exe -command.
5	Run Lua code	Lua code is executed utilizing the statically linked LuaCOM library and the Lua library, model 5.1.5. These libraries, together with the command, weren’t current within the single 32-bit model of the LunarWeb backdoor that we noticed.
6	Write file	Specifies the file path and content material to put in writing.
7	Learn file	Makes use of file mapping to entry content material as an alternative of the common ReadFile API.
8	Get sufferer identification by way of WMI	Obtains sufferer identification data utilizing WMI queries, the identical data as described within the Data assortment part.
9	No operation	N/A
10	Replace state entry in third slot	Updates an entry within the state utilized by the backdoor (index 2), adjusting break period earlier than communication loop and after C&C contact failure..
11	Set state content material in first slot	Units the content material of the state within the first slot (index 0), however its function is unknown.
12	Set state content material in second slot	Units the content material of the state within the second slot (index 1), however its function is unknown.
13	Create course of and get output	Creates an arbitrary course of with a specified command line and retrieves its output by way of a pipe.
14	Zip specified path(s)	Creates a ZIP archive with specified information and directories, by way of the statically linked Zipper library.

A number of the instructions can output an error message referring to the instructions as duties – Format of the duty is inaccurate.

We have been in a position to get well a command bundle that contained a number of shell instructions used for reconnaissance executed by way of command 1, gathering the next: system and OS Data, person data, community configuration and connections, surroundings variables, scheduled duties, put in applications and safety merchandise, firewall settings, listing listings, Kerberos tickets and classes, shared assets, Group Coverage, and native group memberships. Moreover, a learn file command (7) was used to retrieve Zabbix configuration from a specified file path.

Stage 2 payload #2 – LunarMail backdoor

The second backdoor, which we name LunarMail, shares many similarities with LunarWeb. The principle distinction is the communication technique – LunarMail makes use of electronic mail for communication with its C&C server.

This backdoor is designed to be deployed on person workstations, not servers – as a result of it’s continued and meant to run as an Outlook add-in. A high-level overview of how LunarMail operates is proven in Determine 5.

LunarMail shares concepts of its operation with LightNeuron, one other Turla backdoor that makes use of electronic mail messages for C&C functions. Though each use the same exfiltration technique, we didn’t discover any code similarities between the 2 backdoors. Different Turla backdoors with comparable operation embody Outlook backdoor.

Initialization

Throughout its initialization, the backdoor decrypts a string used to initialize a regex object that’s used as a filter to seek for the e-mail profile to make use of for C&C functions, which we describe later. The regex expression, and different strings within the backdoor, are encrypted utilizing RC4 with the static key E3 7C 9E B0 DF D1 46 48 B4 AE 8A 5F 2A A1 78 7B.

To work together with Outlook, the backdoor dynamically resolves the mandatory Outlook Messaging API (MAPI) capabilities.

On every run, the backdoor creates a listing within the path %TEMP%{<random_guid>}, used as a staging listing for knowledge exfiltration.

Configuration and state

Much like LunarWeb, LunarMail’s configuration entries are hardcoded within the binary. It additionally maintains a state file, with a single state (not like LunarWeb, which has a number of state slots).

The configuration doubtless consists of circumstances to search out an Outlook profile for C&C communications, default exfiltration configuration, and the backdoor’s lifespan restrict.

The state is continued within the file %LOCALAPPDATApercentMicrosoftOutlookoutlk.share with a 668-byte construction, up to date throughout execution. It shops, amongst others, a timestamp of the final executed command and present staging listing. On subsequent runs, the earlier staging listing is deleted and changed with a brand new one.

Data assortment

On first run, the LunarMail backdoor collects the next data:

• surroundings variables, and
• recipients of all despatched electronic mail messages (electronic mail addresses).

Moreover, a batch file with shell instructions to acquire additional system data is decrypted however by no means executed.

In sure error instances, comparable to failure to gather the aforementioned data, the e-mail addresses of obtainable Outlook profiles are collected.

Communication and instructions

Working inside Outlook, the LunarMail backdoor communicates with its C&C server – receiving instructions and exfiltrating knowledge – utilizing electronic mail messages, by way of the Outlook Messaging API (MAPI).

Profile search

To speak, LunarMail first searches for appropriate Outlook profiles offered by Microsoft Alternate. The profile circumstances embody having solely 4 default folders (Inbox, Despatched, Deleted, and Outbox), containing the area of the focused establishment within the electronic mail tackle, and never matching a regex sample for varied official institutional emails.

The primary matching profile sends preliminary data. For additional communication, the inboxes of profile candidates are looked for command-containing emails. This strategy avoids hardcoding profiles and makes identification more durable. Moreover, instructions can set a selected profile to make use of, which is continued within the backdoor’s state.

Receiving instructions

LunarMail identifies a profile with instructions by looking out electronic mail messages and making an attempt to parse their attachments. The attachment should be a single PNG picture with the .png extension, with the dimensions of lower than or equal to 10 MB. It then makes an attempt to parse IDAT chunks of the PNG file, on the lookout for an AES seed, an exfiltration configuration, and instructions chunks. All these elements are zlib-compressed and encrypted, the primary utilizing RSA-4096 and the latter two utilizing AES.

Curiously, the chunks should adhere to the PNG format with verified CRCs, leading to a sound, however noisy-looking picture as a result of encrypted, compressed content material.

LunarMail makes use of the identical cryptography as LunarWeb, together with the Mbed TLS library, two RSA-4096 keys (listed in our GitHub repository), and utilization of AES-256 with the identical key derivation algorithm. The decompressed chunk with AES-encrypted content material has the same construction to that seen in LunarWeb.

The decrypted, decompressed exfiltration configuration has a selected construction together with configuration ID, electronic mail tackle, topic, physique, and attachment identify and extension.

The exfiltration configuration construction mirrors LunarWeb’s command bundle metadata, specifying the command outputs’ vacation spot and an ID to keep away from duplicate instructions, saved in state. As soon as decrypted and decompressed, LunarMail instructions have a construction equivalent to LunarWeb’s. Every parsed command is executed, storing output within the staging listing for exfiltration.

Notably, electronic mail messages that fail parsing for instructions have their IDs cached to keep away from repeated parsing, though the cache just isn’t continued and it’s recreated on every backdoor execution. Emails efficiently parsed for instructions are deleted after processing.

Instructions

When it comes to command capabilities, LunarMail is easier and includes a subset of the instructions present in LunarWeb. It could possibly write a file, create a brand new course of, and uniquely, take a screenshot and modify the C&C communication electronic mail tackle. Whereas LunarMail lacks separate instructions for operating shell or PowerShell instructions, it does assist Lua scripts. When executed, instructions write their output to information within the staging listing.

The total record of supported instructions is proven in Desk 5.

Desk 5. Overview of LunarMail instructions

Sort	Command	Particulars
0	No operation	N/A
1	Write file	Specifies the file path and content material to put in writing.
2	Set the e-mail tackle used for C&C communications	Units a selected Outlook profile to make use of for C&C communications. The profile is specified by an electronic mail tackle, which is then continued within the backdoor’s state.
3	Create course of and get output	Creates an arbitrary course of with a specified command line, redirecting its output to the staging listing.
4	Take a screenshot	Makes use of GDI+ API to seize all the display and produce a JPG file.
5	Run Lua code	Simply as in LunarWeb, Lua code is executed utilizing the statically linked libraries LuaCOM and Lua.

Exfiltrating knowledge – preparation

LunarMail searches its staging listing for output information produced by the backdoor, getting ready them for exfiltration by embedding them in a PNG picture or PDF doc (relying on the attachment extension within the exfiltration configuration). Each PNG and PDF information are created utilizing a sound content material template.

For PNG information, a template matching the compromised establishment’s emblem is used, indicating prior information and preparation of the backdoor. To create a PNG that comprises output information, LunarMail first generates a random 32-byte AES seed, used for encryption. Then it creates IDAT chunks with knowledge and appends them to the PNG template. The chunks are much like obtained instructions, containing the next:

• Chunk with AES seed – RSA-4096 encrypted, zlib compressed.
• Chunk(s) with filename and content material – AES-256 encrypted, zlib compressed.

Earlier than compression and encryption, the output file identify and content material are wrapped right into a construction that additionally comprises a magic string 001035 that might be the backdoor model. Similar to in obtained command PNGs, the created chunks comply with the PNG specification and have their CRC checksum calculated, making certain a sound picture. To finalize the picture, the IEND footer chunk is appended.

The second technique, producing a PDF file, makes use of an encrypted template from the file %TEMPpercentl4_mgrT.tmp. We’ve got not noticed this knowledge file and the template’s content material is unknown, however in all probability it’s a benign, unsuspicious doc.

The output information with metadata are inserted on the finish of the final stream within the PDF template, earlier than the terminating endstream key phrase. They’re inserted within the following format and order:

1. Output information – variable sized, zlib compressed, AES-256 encrypted.
2. Metadata – fastened measurement (512 bytes), RSA-4096 encrypted.

The output filename and content material are wrapped into the identical construction as with the PNG, together with the magic string, which is then compressed and encrypted.

The metadata comprises data essential for parsing and decrypting the buildings of output information, together with AES seed and output file positions within the PDF file.

After processing and embedding within the PNG or PDF file, information staged for exfiltration are deleted. The created file quickly resides within the staging listing till exfiltration.

Exfiltrating knowledge – transmission

Ready PNG photographs or PDF paperwork containing output information are transmitted as attachments in emails to an attacker-controlled inbox, as per the exfiltration configuration. The default LunarMail setup features a particular recipient electronic mail, topic header, message physique, and attachment filename. The e-mail content material, though within the language of the compromised European MFA, seems machine translated as a result of its unnatural phrasing.

An exfiltration configuration from a obtained command overrides the default one. We’ve got not recovered any instructions so don’t know if completely different electronic mail recipients, topics, our bodies, or attachment identify or sorts are used throughout a number of instructions.

If supported, the e-mail physique makes use of HTML format. The PNG is embedded as a picture within the physique, not like the PDF. Determine 6 exhibits an illustration of an exfiltration electronic mail based mostly on the default configuration. The e-mail was translated, redacted, and the emblem was modified by ESET Analysis, to not reveal the compromised establishment.

Exfiltration electronic mail messages are despatched with the PR_DELETE_AFTER_SUBMIT flag. As well as, any despatched messages to the exfiltration tackle are deleted.

Conclusion

We’ve got described two beforehand unknown backdoors utilized in compromises of a European authorities’s establishments, which we attribute with medium confidence to the Russia-aligned APT group Turla.

The backdoors share a loader, bear code overlaps, and assist comparable instructions, however they undertake completely different C&C communication strategies. The primary backdoor – LunarWeb – makes use of HTTP(S) and makes an attempt to mix in by mimicking the site visitors of official companies comparable to Home windows Replace. The second backdoor – LunarMail – piggybacks on Outlook and communicates by way of electronic mail messages, utilizing both PNG photographs or PDF paperwork to exfiltrate knowledge.

We noticed various levels of sophistication within the compromises; for instance, the cautious set up on the compromised server to keep away from scanning by safety software program contrasted with coding errors and completely different coding kinds (which aren’t the scope of this blogpost) within the backdoors. This implies a number of people have been doubtless concerned within the improvement and operation of those instruments.

Though the described compromises are newer, our findings present that these backdoors evaded detection for a extra prolonged interval and have been in use since at the least 2020, based mostly on artifacts discovered within the Lunar toolset.

IoCs

A complete record of IoCs and samples might be present in our GitHub repository.

Recordsdata

SHA-1	Filename	Detection	Description
DE83C2C3FE68CB1BF961 73E9EE3EA6161DCFB24A	App_Web_0bm4blbr.dll	MSIL/Agent.ERT	Compiled model of ASP.NET net web page that installs LunarWeb.
9CEC3972FA35C88DE87B D66950E18B3E0A6DF77C	N/A	VBA/TrojanDownloader. Agent.ZJC	Malicious Phrase macro that installs LunarMail.
2ED792E39F7D56DE52BD F4AED96AFC898478BFDF	gpgol.dll	Win64/LunarLoader.B	LunarLoader (x64) used to load LunarMail.
F09E36553E48EBD42E60 D9B25A390C0F57FF8DE0	gpgol.dll	Win32/LunarLoader.A	LunarLoader (x86) used to load LunarMail.
94A4CE9C75BC847E7BE5 9B96C4133D677D909414	tapiperf.dll	Win64/LunarLoader.C	LunarLoader (x64) used to load LunarWeb.
00006B30806F91591134 9D82BEEB1AEB9025ADB4	admpwd.dll	Win64/LunarLoader.A	LunarLoader (x64); a trojanized AdmPwd, used to load LunarWeb.
19D86CF2ED82EAE23E01 9706FAE8DAFC60552E85	AdmPwd.dll	Win64/LunarLoader.A	LunarLoader (x64); a trojanized AdmPwd, used to load LunarWeb.
795C4127D42FE8DFAF45 10B406B52BA5BEDE8D3A	winnet.dll.mui	Win64/LunarLoader.B	LunarLoader (x64) used to load LunarWeb.
754FB657156643FD09A6 8EC9FC124528578CAB0C	N/A	Win32/LunarWeb.A	LunarWeb backdoor (x86).
FCAE66F6D95C78DC8296 88CC0F4C39BB5A57828B	N/A	Win64/LunarMail.A	LunarMail backdoor (x64).
67C6AEC8D129E610378E F52F8BF934886587932F	N/A	Win32/LunarMail.A	LunarMail backdoor (x86).
4C84110F1B10DF5FDD61 2759E210E44B0F0505EF	N/A	Win64/LunarWeb.A	LunarWeb backdoor (x64).
5D3975E57BDCB630A00F EBE5D405EEFB6D119D86	N/A	Win64/LunarWeb.A	LunarWeb backdoor (x64).
5EF771AFC96C24371D36 7448627609CFACB34A57	N/A	Win64/LunarWeb.A	LunarWeb backdoor (x64).
512E4FA7D6119270FF44 A3B2A2359EE8825392EF	N/A	Win64/LunarWeb.A	LunarWeb backdoor (x64).

File paths

Stage 2 blob

C:WindowsSystem32DynamicAuth.bin

C:Program FilesLAPSCSEadmpwd.cache

C:ProgramDataMicrosoftWinThumbadcache.clb

C:WindowsSystem32perfcache.dat

%USERPROFILEpercentGpg4wintempkeys.dat

LunarWeb state file

C:ProgramDataMicrosoftWindowsTemplatescontent.tpl

C:ProgramDataMicrosoftWinThumbthumb.clb

C:ProgramDataMicrosoftWinThumbcfcache.clb

C:WindowsSystem32perfconfm.dat

LunarMail state file

%LOCALAPPDATApercentMicrosoftOutlookoutlk.share

Community

IP	Area	Internet hosting supplier	First seen	Particulars
N/A	thedarktower.av. grasp.dns-cloud[.]web	N/A	2020‑02‑01	Area (Free DNS) pinged by malicious Phrase macro.
45.33.24[.]145	N/A	Akamai Linked Cloud	2020‑05‑20	C&C server of LunarWeb (compromised VPS).
45.79.93[.]87	N/A	Akamai Linked Cloud	2020‑05‑20	C&C server of LunarWeb (compromised VPS).
65.109.179[.]67	N/A	Hetzner On-line GmbH	2023‑10‑29	C&C server of LunarWeb (compromised VPS).
74.50.80[.]35	N/A	Host Division NJ, LLC	2023‑10‑29	C&C server of LunarWeb.
82.165.158[.]86	N/A	IONOS SE	2022‑08‑03	C&C server of LunarWeb (compromised VPS).
82.223.55[.]220	N/A	IONOS SE	2022‑08‑03	C&C server of LunarWeb (compromised VPS).
139.162.23[.]113	N/A	Akamai Linked Cloud	2023‑06‑15	C&C server of LunarWeb (compromised VPS).
158.220.102[.]80	N/A	Contabo GmbH	2023‑10‑29	C&C server of LunarWeb.
161.97.74[.]237	N/A	Contabo GmbH	2023‑06‑15	C&C server of LunarWeb.
176.57.150[.]252	N/A	Contabo GmbH	2023‑06‑15	C&C server of LunarWeb.
212.57.35[.]174	N/A	Webglobe, a.s.	2023‑06‑02	C&C server of LunarWeb (compromised VPS).
212.57.35[.]176	N/A	Webglobe, a.s.	2023‑06‑02	C&C server of LunarWeb (compromised VPS).

Registry keys

HKCUSOFTWAREClassesCLSID{3115036B-547E-4673-8479-EE54CD001B9D}

MITRE ATT&CK methods

This desk was constructed utilizing model 15 of the MITRE ATT&CK framework.

Tactic	ID	Identify	Description
Reconnaissance	T1591	Collect Sufferer Org Data	LunarMail’s communication technique signifies prior information about compromised establishments.
Useful resource Improvement	T1583.002	Purchase Infrastructure: DNS Server	Stage 0 macro pings a website from free DNS internet hosting offered by ClouDNS.
	T1583.003	Purchase Infrastructure: Digital Non-public Server	Turla has used VPS internet hosting suppliers for C&C servers.
	T1584.003	Compromise Infrastructure: Digital Non-public Server	Turla has used compromised VPSes for C&C functions.
	T1586.002	Compromise Accounts: Electronic mail Accounts	Turla has used doubtless compromised electronic mail accounts for communication with the LunarMail backdoor.
	T1587.001	Develop Capabilities: Malware	Turla has developed customized malware, together with loaders and backdoors.
Execution	T1047	Home windows Administration Instrumentation	LunarWeb obtains system data by utilizing WMI queries.
	T1059	Command and Scripting Interpreter	LunarWeb and LunarMail can execute Lua scripts.
	T1059.001	Command and Scripting Interpreter: PowerShell	LunarWeb can execute PowerShell instructions.
	T1059.003	Command and Scripting Interpreter: Home windows Command Shell	LunarWeb can execute shell instructions by way of cmd.exe.
	T1059.005	Command and Scripting Interpreter: Visible Fundamental	Stage 0 Phrase doc comprises a VBA macro.
	T1106	Native API	LunarWeb and LunarMail use varied Home windows APIs.
	T1204.002	Person Execution: Malicious File	Stage 0 Phrase doc with malicious macro should be opened by sufferer.
Persistence	T1137.006	Workplace Utility Startup: Add-ins	LunarMail loader is continued as an Outlook add-in.
	T1547	Boot or Logon Autostart Execution	A LunarWeb loader is continued as a Group Coverage extension.
	T1574	Hijack Execution Move	A LunarWeb loader is continued by changing the system DLL tapiperf.dll.
Protection Evasion	T1027	Obfuscated Recordsdata or Data	LunarWeb and LunarMail are AES-256 encrypted on disk.
	T1027.003	Obfuscated Recordsdata or Data: Steganography	LunarMail levels exfiltration knowledge right into a PNG picture or PDF doc.
	T1027.007	Obfuscated Recordsdata or Data: Dynamic API Decision	LunarMail dynamically resolves MAPI capabilities.
	T1027.009	Obfuscated Recordsdata or Data: Embedded Payloads	LunarMail installer has payloads embedded in a DOCX format doc.
	T1036.005	Masquerading: Match Reputable Identify or Location	Filenames utilized by LunarWeb and LunarMail loading chains mimic official information.
	T1070.004	Indicator Removing: File Deletion	LunarWeb and LunarMail can uninstall themselves by deleting their loading chain.
	T1070.008	Indicator Removing: Clear Mailbox Knowledge	LunarMail deletes electronic mail messages used for C&C communications.
	T1140	Deobfuscate/Decode Recordsdata or Data	LunarWeb and LunarMail decrypt their strings utilizing RC4.
	T1480.001	Execution Guardrails: Environmental Keying	LunarLoader decrypts its payload utilizing a key derived from the DNS area identify.
	T1620	Reflective Code Loading	LunarWeb and LunarMail are executed utilizing a reflective loader.
Discovery	T1007	System Service Discovery	LunarWeb retrieves a listing of companies.
	T1016	System Community Configuration Discovery	LunarWeb retrieves community adapter data.
	T1057	Course of Discovery	LunarWeb retrieves a listing of operating processes.
	T1082	System Data Discovery	LunarWeb retrieves system data comparable to OS model, BIOS model, area identify, and surroundings variables. LunarMail retrieves surroundings variables.
	T1518.001	Software program Discovery: Safety Software program Discovery	LunarWeb discovers put in safety options by way of the WMI question wmic /Namespace:rootSecurityCenter2 Path AntiVirusProduct Get *.
Assortment	T1005	Knowledge from Native System	LunarWeb and LunarMail can add information from the compromised machine.
	T1074.001	Knowledge Staged: Native Knowledge Staging	LunarMail levels knowledge in a listing in %TEMP%.
	T1113	Display Seize	LunarMail can seize screenshots.
	T1114.001	Electronic mail Assortment: Native Electronic mail Assortment	LunarMail collects recipients of despatched electronic mail messages and may accumulate electronic mail addresses of Outlook profiles.
	T1560.002	Archive Collected Knowledge: Archive by way of Library	LunarWeb and LunarMail use a statically linked zlib library for compression of collected knowledge.
Command and Management	T1001.002	Knowledge Obfuscation: Steganography	LunarWeb can obtain instructions hidden in JPG or GIF photographs. LunarMail receives instructions hidden in PNG photographs and exfiltrates knowledge hidden in PNG photographs or PDF paperwork.
	T1001.003	Knowledge Obfuscation: Protocol Impersonation	LunarWeb impersonates official domains in C&C communications by utilizing a faux Host header and identified URIs.
	T1071.001	Utility Layer Protocol: Internet Protocols	LunarWeb makes use of HTTP for C&C communications.
	T1071.003	Utility Layer Protocol: Mail Protocols	LunarMail makes use of electronic mail messages for C&C communications.
	T1090.001	Proxy: Inner Proxy	LunarWeb can use an HTTP proxy for C&C communications.
	T1095	Non-Utility Layer Protocol	Stage 0 macro pings the C&C server, using ICMP protocol.
	T1132.001	Knowledge Encoding: Customary Encoding	LunarWeb might obtain base64-encoded knowledge from the C&C server.
	T1573.001	Encrypted Channel: Symmetric Cryptography	LunarWeb and LunarMail encrypt C&C communications utilizing AES-256.
	T1573.002	Encrypted Channel: Uneven Cryptography	LunarWeb and LunarMail encrypt the AES key utilized in C&C communications utilizing RSA-4096.
Exfiltration	T1020	Automated Exfiltration	LunarWeb and LunarMail robotically exfiltrate collected knowledge to the C&C server.
	T1030	Knowledge Switch Measurement Limits	LunarWeb splits exfiltrated knowledge above 1.33 MB into a number of smaller chunks. LunarMail limits the dimensions of electronic mail attachments containing exfiltrated knowledge.
	T1041	Exfiltration Over C2 Channel	LunarWeb and LunarMail exfiltrate knowledge over the C&C channel.