The novel method of reading commands from seemingly innocent Internet Information Services (IIS) logs has been used to install backdoors and other tools by a recently leaked dropper. Cybersecurity experts at Symantec claimed an attacker is utilizing the malware known as Cranefly also known as UNC3524 to install Trojan. Danfuan, another undocumented malware, as well as other tools.
Mandiant reported that Cranefly mainly targeted the emails of individuals who specialized in corporate development, merger and acquisitions, and significant corporate transactions when it was originally founded in May. Mandiant claims that these attackers remained undetected on target networks for at least 18 months by using backdoors on equipment without support for security measures.
One of the main malware strains used by the gang is QUIETEXIT, a backdoor installed on network equipment like cloud services and wireless access point controllers that do not enable antivirus or endpoint monitoring. This allows the attacker to remain undetected for a long time.
Geppei and Danfuan augment Cranefly's arsenal of specialized cyber weapons, with Geppei serving as a dropper by collecting orders from IIS logs that look like normal web access requests delivered to a compromised host.
The most recent Symantec advisory now claims that UNC3524 used Hacktool-based backdoors in some instances. Multiple advanced persistent threat (APT) clusters use the open-source technology Regeorg.
Additionally, Symantec has cautioned that Cranefly is a 'pretty experienced' hacking group as evidenced by the adoption of a new method in conjunction with the bespoke tools and the measures made to conceal their activity.
On its alert and Protection Bulletins website, Symantec lists the indicators of compromise (IoC) for this attack. Polonium is another threat actor that usually focuses on gathering intelligence, and ESET recently saw Polonium utilizing seven different backdoor variants to snoop on Israeli firms.
Cranefly employs this sneaky method to keep a foothold on compromised servers and gather information covertly. As attackers can send commands through various channels, including proxy servers, VPNs, Tor, or online development environments, this method also aids in avoiding detection by investigators and law enforcement.
It is unclear how many systems have been compromised or how often the threat actors may have utilized this technique in ongoing operations.
