Ransomware Gangs Adopt New Techniques To Avoid Detection

Fraud Management & Cybercrime , Next-Generation Technologies & Secure Development , Ransomware

LockFile Ransomware Using New Techniques to Evade Detection

Sophos: Methods Include ‘Intermittent Encryption’

Visual comparison of the same text certificate encrypted by DarkSide and LockFile (Source: Sophos)

The operators of LockFile ransomware have adopted new techniques, including “intermittent encryption,” to help evade detection, according to cybersecurity firm Sophos.

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For example, the ransomware gang is only partially encrypting documents. Partial encryption is generally used by ransomware operators to speed upwardly the encryption procedure; this technique has previously been implemented by BlackMatter, DarkSide and LockBit two.0, says Mark Loman, director of engineering science at Sophos and the writer of the research report.

“What sets LockFile apart is that, dissimilar the others, it doesn’t encrypt the first few blocks. Instead, LockFile encrypts every other 16 bytes of a document. This means that a file such equally a text document remains partially readable and looks statistically like the original,” Loman says.

The technique, dubbed “intermittent encryption,” apparently hasn’t been used in other ransomware attacks, Sophos reports.

This approach can prove constructive in evading detection past software that relies on inspecting content using statistical analysis to discover encryption, a researcher says.

Sophos detected the new technique while analyzing a file on VirusTotal. VirusTotal allows users to analyze suspicious files and URLs to detect malware and share it with the security community.

LockFile was beginning detected in April, when it exploited ProxyShell vulnerabilities in on-bounds Microsoft Exchange servers, reported researchers from Tendency Micro. Information technology as well deployed a PetitPotam NTLM relay assault to seize control of the domain.

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Other New Evasion Techniques

The LockFile ransomware also uses a relatively uncommon process known as “memory mapped input/output” to encrypt a file, the Sophos report points out.

“This technique allows the ransomware to invisibly encrypt documents that are buried in the computer’s memory without creating additional input/output telematic traffic that detection technologies will spot,” the report says.

This technique has previously been used past WastedLocker and Maze ransomware.

LockFile also doesn’t need to connect to a control-and-control center to communicate, which reduces traffic and helps go on the assail activity under the detection radar, the Sophos report states.

“Once the ransomware has encrypted all the documents on the machine, it deletes itself. This means that, after the attack, there is no ransomware binary for incident responders or endpoint protection software to find or clean upward,” co-ordinate to the study.

LockFile as well avoids encrypting some 800 different filetypes by extension, further confusing certain anti-ransomware protections, the study adds.


To help mitigate risks, Sophos recommends separating critical servers from each other and from workstations by putting them into separate VLANs, regularly auditing Active Directory to ensure that no one have more access than is needed for their purpose, and double-checking that the patches applied have been installed correctly and are in identify for critical systems such as cyberspace-facing machines or domain controllers.

Although previous malware attacks have used some of the techniques that the gang backside LockFile is now using, it’s unusual to run across all these techniques implemented in the same ransomware campaign, says Sean Nikkel, senior cyberthreat intel analyst at cybersecurity firm Digital Shadows.

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“Information technology puts the onus on defenders to also investigate more organisation processes that are performing this kind of behavior, which potentially means an increase in faux positives and time to investigate,” he says.

Attackers can use whatsoever additional time before detection to increase their chances of success, Nikkel says.

“Some malware may only need seconds to minutes to be successful, just quieter attacks similar [LockFile] may increase potential dwell time for an attacker to be in a network,” he says. “This, in plough, may allow more fourth dimension to reconnoiter the network and attack more disquisitional data.”

Oliver Tavakoli, CTO of cybersecurity company Vectra AI, says the encryption phase of a ransomware attack is oft very quick, taking anywhere from a few minutes to a few hours.

Most attacks, Tavakoli says, get all the pieces in place before kickoff simultaneous encryption of files from all the commandeered machines.

“Many of the elements of ransomware attacks are detectable well earlier the encryption stage – or the exfiltration stage, which precedes encryption – kicks into action,” he says.

That’southward why organizations should build endpoint and network detection and response capabilities with a focus on reconnaissance, lateral movement and command-and-command activity, he adds.

Ransomware Gangs Adopt New Techniques To Avoid Detection

Source: https://www.bankinfosecurity.com/lockfile-ransomware-using-new-techniques-to-evade-detection-a-17442