Agent Tesla's Added New Tools & Tactics to Its Arsenal
The persistent notion money and the threat actors extra and extra turning into extra subtle are riding the alarming price of malware replace.
Every day, new forms of malware are created and put into circulation at an distinctive velocity, the utilization of as a lot as the moment tricks to abet a long way off from discovery and overcome security programs, while taking abet of basically the newest gadget vulnerabilities.
Cybersecurity researchers at Trustwave recently identified that the operators of Agent Tesla added new tools and ways to its arsenal.
Agent Tesla’s Unique Tools & Ways
To ship and hang malicious actions that facilitate prison actions, threat actors necessitate malware loaders.
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These loaders expend subtle evasion programs to evade safety features and take abet of varied distribution networks.
On March Eighth, 2024, a phishing email used to be identified by SpiderLabs which trigger off an infection chain ensuing in Agent Tesla being deployed.
The infection began when a phishing email posed as a monetary institution fee notification and delivered an obfuscated, polymorphic loader.
To guide clear of detection, this loader fetched its payload by proxies the utilization of heaps of URLs and user brokers before executing the Agent Tesla infostealer in memory.
All recordsdata used to be stolen by Agent Tesla which then despatched it by hacked email accounts for secret verbal replace capabilities.
The assault employs a phishing email with a malicious .tar.gz attachment masquerading as a monetary institution fee receipt.
It contains a polymorphic .NET loader that obfuscates and encrypts its configuration recordsdata the utilization of heaps of decryption routines across variants.
The loader decrypts strings by index-essentially based mostly matching of encrypted recordsdata with keys.
It evades detection by programs love packing, obfuscation, memory permission changes, and AMSI bypassing.
Key phrases instruct it reflectively hundreds additional payloads from a URL laid out in the encrypted configuration, reads the record.
To facilitate stealthy payload execution, the loader bypasses AMSI, prepares memory build, and retrieves the payload from a particular URL the utilization of an outlined user-agent string.
One variant employs an commence-provide proxy record for obfuscated payload provide.
The loader extracts the encoded payload from HTML the utilization of delimiters, decrypts it via XOR with an embedded key, and reflectively hundreds the Agent Tesla infostealer into memory by invoking its entry point – all while avoiding disk artifacts for evasiveness.
Agent Tesla is a memory-resident recordsdata stealer that conducts keystroke logging, credential theft, and recordsdata exfiltration via SMTP, in total leveraging compromised email accounts for stealthy verbal replace.
This new Agent Tesla variant employs a .NET loader the utilization of fake attachment phishing, obfuscation, polymorphic decryption, AMSI bypassing, and reflective loading for evasive payload execution fully in memory.
The versatile loader’s evolution suggests the aptitude for deploying other malware payloads beyond aesthetic Agent Tesla going forward.
IoCs
Loader (Variant 1)
MD5 b69f65b999db695b27910689b7ed5cf0
SHA256 ab9cd59d789e6c7841b9d28689743e700d492b5fae1606f184889cc7e6acadcc
Loader (Variant 2)
MD538d6ebb40197248bc9149adeec8bd0e7
SHA256a02388b5c352f13334f30244e9eedac3384bc2bf475d8bc667b0ce497769cc6a
Packed Agent Tesla
MD52bd452c46a861e59ac151a749047863f, 63f802e47b78ec3d52fe6b403bad823f
SHA256 e3cb3a5608f9a8baf9c1da86324474739d6c33f8369cc3bb2fd8c79e919089c4, f74e1a37a218dc6fcfabeb1435537f709d742505505a11e4757fc7417e5eb962
Unpacked Agent Tesla
MD5 3637aa1332b312fe77cc40b3f7adb8dc, 37b38ae2d99dd5beb08377d6cbd1bccd
SHA256 3a1fe17d53a198f64051a449c388f54002e57995b529635758248dc4da7f5080, a3645f81079b19ff60386cb244696ea56f5418ae556fba4fd0afe77cfcb29211
SMTP Exfiltration
Sender email: merve@temikan[.]com[.]tr
Receiver email: frevillon[.]acsitec@proton[.]me
Fetch URLs
hxxps[://]artemis-rat[.]com/rep/65f0e7dd5b705f429be16c65
hxxps[://]artemis-rat[.]com/rep/65eb0afe3a680a9851f23712
Client-Agent
Mozilla/5.0 (Home windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, killer Gecko) Chrome/58.0.3029.110 Safari/537.3
Record of Proxy Servers
hxxps[://]github[.]com/TheSpeedX/PROXY-Record/blob/master/hxxp[.]txt
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