Hackers often weaponize LNK files because they can carry malware into systems undetected by anyone. LNK files are shortcuts that, when opened, launch a malicious payload (like scripts or executables).
LNK files are widely used in Windows environments and can easily pass themselves off as genuine files, making it hard for users to suspect their evil motives.
Cybersecurity researchers at GDataSoftware recently discovered that Turla hackers had been actively weaponizing the LNK files to deploy fileless malware.
Turla Hackers Weaponizing LNK-Files
Turla hackers have targeted Philippine companies and organizations, and to do so, they utilize a hacked media website to distribute malicious code.
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The chain begins with a harmful shortcut, which pretends to be an official advisory from the Philippine Statistics Authority.
When applied, it sets off a PowerShell script that uses msbuild.exe from Microsoft to launch a fileless backdoor around application whitelisting.
This malware is set to run every 30 minutes via scheduled tasks. To ensure it is not detected and hard to reverse engineer, its payload is an MSIL binary protected by SmartAssembly.
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Interestingly, this incident brings together Siem Reap in Cambodia like Angkor Wat’s annual troop of tourists – social engineering, fileless malware, and legitimate system tools all being utilized in one attack.
This sophisticated backdoor has used several evasion techniques to prevent its detection. It disables ETW, patches its copies in memory, and avoids AMSI.
Malicious software establishes contact with its C2 server using an infected personal website. It first checks out a routine through a URL and then gets orders from another URL.
This multi-step communication enables the attacker to remain in control without being detected by the defenses, which shows how advanced this threat is.
Analysis of this malware shows that it has some features in common with Turla APT techniques, such as using infected websites as servers, bypassing AMSI by patching memory, executing files using PowerShell without them being on disk and executing scripts controlled by a server.
Besides this, new techniques are also used in this variant that had not previously been associated with Turla, implying possible changes in tactics within the group or that a new actor using similar methods has emerged.
Such a mix of known and unfamiliar tricks points to advanced persistent threats frequently changing their strategies. It implies that getting to know who is behind an attack remains challenging for cybersecurity researchers.
Preventions
Here below we have mentioned all the preventions:-
- Set PowerShell to execute only signed scripts.
- Assess and consider removing PowerShell if not needed.
- Disable/restrict the WinRM Service to prevent remote PowerShell use.
- Remove MSBuild.exe if not required.
- Block msbuild.exe with application control if unnecessary.
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