In an analysis published by Cybereason researchers yesterday, the Evilnum group has not only tweaked its infection chain but has also deployed a Python RAT called "PyVil RAT," which possesses abilities to gather information, take screenshots, capture keystrokes data, open an SSH shell and deploy new tools.
"Since the first reports in 2018 through today, the group's TTPs have evolved with different tools while the group has continued to focus on fintech targets," the cybersecurity firm said.
"These variations include a change in the chain of infection and persistence, new infrastructure that is expanding over time, and the use of a new Python-scripted Remote Access Trojan (RAT)" to spy on its infected targets.
Back in July, the APT group was found targeting companies with spear-phishing emails that contain a link to a ZIP file hosted on Google Drive to steal software licenses, customer credit card information, and investments and trading documents.
While the modus operandi of gaining an initial foothold in the compromised system remains the same, the infection procedure has witnessed a major shift.
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The multi-process delivery procedure ("ddpp.exe"), upon execution, unpacks shellcode to establish communication with an attacker-controlled server and receive a second encrypted executable ("fplayer.exe") that functions as the next stage downloader to fetch the Python RAT.
"In previous campaigns of the group, Evilnum's tools avoided using domains in communications with the C2, only using IP addresses," the researchers noted. "While the C2 IP address changes every few weeks, the list of domains associated with this IP address keeps growing."
While Evilnum's exact origins still remain unclear, it's evident that their constant improvisation of TTPs has helped them stay under the radar.
As the APT's techniques continue to evolve, it's essential that businesses remain vigilant and employees monitor their emails for phishing attempts and exercise caution when it comes to opening emails and attachments from unknown senders.