Stealthy Malware Has Infected Thousands of Linux Systems for Years

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After exploiting a vulnerability or misconfiguration, the exploit code downloads the primary payload from a server, which, most often, has been hacked by the attacker and transformed right into a channel for distributing the malware anonymously. An assault that focused the researchers’ honeypot named the payload httpd. As soon as executed, the file copies itself from reminiscence to a brand new location within the /temp listing, runs it, after which terminates the unique course of and deletes the downloaded binary.

As soon as moved to the /tmp listing, the file executes beneath a distinct title, which mimics the title of a identified Linux course of. The file hosted on the honeypot was named sh. From there, the file establishes an area command-and-control course of and makes an attempt to realize root system rights by exploiting CVE-2021-4043, a privilege-escalation vulnerability that was patched in 2021 in Gpac, a extensively used open supply multimedia framework.

The malware goes on to repeat itself from reminiscence to a handful of different disk areas, as soon as once more utilizing names that seem as routine system information. The malware then drops a rootkit, a bunch of widespread Linux utilities which were modified to function rootkits, and the miner. In some instances, the malware additionally installs software program for “proxy-jacking,” the time period for surreptitiously routing visitors by means of the contaminated machine so the true origin of the info isn’t revealed.

The researchers continued:

As a part of its command-and-control operation, the malware opens a Unix socket, creates two directories beneath the /tmp listing, and shops knowledge there that influences its operation. This knowledge consists of host occasions, areas of the copies of itself, course of names, communication logs, tokens, and extra log data. Moreover, the malware makes use of atmosphere variables to retailer knowledge that additional impacts its execution and habits.

All of the binaries are packed, stripped, and encrypted, indicating vital efforts to bypass protection mechanisms and hinder reverse engineering makes an attempt. The malware additionally makes use of superior evasion strategies, reminiscent of suspending its exercise when it detects a brand new person within the btmp or utmp information and terminating any competing malware to keep up management over the contaminated system.

By extrapolating knowledge such because the variety of Linux servers related to the web throughout varied providers and functions, as tracked by providers reminiscent of Shodan and Censys, the researchers estimate that the variety of machines contaminated by Perfctl is measured within the 1000’s. They are saying that the pool of weak machines—which means people who have but to put in the patch for CVE-2023-33426 or include a weak misconfiguration—is within the tens of millions. The researchers have but to measure the quantity of cryptocurrency the malicious miners have generated.

Individuals who wish to decide if their gadget has been focused or contaminated by Perfctl ought to search for indicators of compromise included in Thursday’s post. They need to even be looking out for uncommon spikes in CPU utilization or sudden system slowdowns, significantly in the event that they happen throughout idle occasions. Thursday’s report additionally offers steps for stopping infections within the first place.

This story initially appeared on Ars Technica.