Cisco Talos researchers have detected a new malware campaign that is using job lures to deploy malware. The threat actors are weaponizing a year-old remote code execution flaw in Microsoft Office, infecting victims with leaked versions of Cobalt Strike beacons.
According to the researchers, the attacks were discovered in August 2022. It begins with phishing emails regarding the U.S. Government's job details or a New Zealand trade union. The emails comprise of a multistage and modular infection chain with fileless, malicious scripts.
On opening the attached malicious Word file, the victim was infected with an exploit for CVE-2017-0199, a remote code execution vulnerability in MS Office, that allows the threat actor to control the infected systems. As a result, the attacker deploys a chain of attack scripts that leads up to the Cobalt Strike beacon installation.
"The payload discovered is a leaked version of a Cobalt Strike beacon[...]The beacon configuration contains commands to perform targeted process injection of arbitrary binaries and has a high reputation domain configured, exhibiting the redirection technique to masquerade the beacon's traffic" states Cisco Talos researchers Chetan Raghuprasad and Vanja Svajcer in a new analysis published on Wednesday.
In addition to discovering the Cobalt Strike beacon as the payload in this campaign, the researchers have also observed the usage of the Redline information-stealer and Amadey botnet executables as the payloads.
The Modus Operandi has been called “highly modularized” by the experts, the attack stands out for it leverages Bitbucket repositories to deploy malicious content that serves as a kickoff for downloading a Window executable, responsible for the installation of Cobalt Strike DLL beacon, says the Cybersecurity researchers.
"This campaign is a typical example of a threat actor using the technique of generating and executing malicious scripts in the victim's system memory[...]Organizations should be constantly vigilant on the Cobalt Strike beacons and implement layered defense capabilities to thwart the attacker's attempts in the earlier stage of the attack's infection chain." states the researchers.
Considering the growing phishing and malware attacks, the Cisco Talos team suggested users protect themselves with measures, such as updating their software and not opening any attachments in unsolicited messages. Besides, the team also suggests that administrators monitor their network security.
