Raspberry Robin Malware Evolves with Sophisticated Evasion Tactics

The Raspberry Robin malware, a heavily obfuscated Windows worm first identified in late 2021, has become one of the most prevalent threats facing enterprises today. Initially targeting technology and manufacturing organizations through removable media like USB drives, Raspberry Robin has since expanded its distribution methods, concerning cybersecurity experts.

According to HP's Threat Research Team, threat actors have recently been delivering Raspberry Robin through malicious Windows Script Files (WSF). These script files employ a range of anti-analysis techniques to evade detection.

Jason Soroko, Senior Vice President of Product at Sectigo, discussed the sophistication of this malware. "The obfuscation techniques used by this malware payload system are impressive. To be able to hide code patterns, as well as behavior after execution from endpoint protection, takes some clever thinking," Soroko said.

Balazs Greksza, Threat Response Lead at Ontinue, added, "Raspberry Robin developers are active and lately have been using 1-day vulnerabilities for privilege escalation. They also recently improved anti-emulation/sandbox evasions using VDLL checks." Greksza mentions that while the WSF downloader currently evades most defenses, "the delivered threats have a higher chance of eventually being caught and prevented at runtime."

Once on a system, Raspberry Robin can download and execute additional payloads, serving as an initial access broker for other malware families like SocGholish, Cobalt Strike, IcedID, BumbleBee, Truebot, and even human-operated ransomware. Ravisankar Ramprasad, Threat Researcher at Menlo Security, warned, "This malware acts as an Initial Access Broker (IAB) or downloader for other malware or even ransomware."

A concerning aspect is Raspberry Robin's ability to exploit Windows privilege escalation vulnerabilities. As Ramprasad stated, "Raspberry Robin is known for its ability to exploit 1-day vulnerabilities, particularly the privilege escalation vulnerabilities affecting Windows systems."

The malware has also demonstrated a shift in its targets, moving from initially focusing on IoT devices to now targeting central Windows systems. John Gallagher, Vice President of Viakoo Labs, commented, "It could be that IoT-based delivery was the warm-up act to the main event; IoT systems are often on hidden or segmented networks, and by moving to Windows systems there will be more opportunities for exploitation."

Perhaps most concerning are the anti-detection methods employed by Raspberry Robin. Gallagher noted, "Most troubling is the sophisticated anti-detection methods used by Raspberry Robin, making testing in a sandbox ineffective." As a result, he suggested, "Organizations should consider other restrictions on Windows Script Files until a better method of early detection is available."

Security experts agree that countering this evasive and evolving malware early in the infection chain should be a top priority for enterprises. With its ability to lead to more severe threats like ransomware, and to adopt new distribution and obfuscation tactics frequently, Raspberry Robin poses an increasing danger that requires new defensive approaches from security teams.

Source: SecureWorld | Drew Todd