Linux Machines with Poorly Secured SSH Servers are Under Attack

Dec 29, 2023

A new cryptocurrency miner is attacking Linux servers to co-opt them into a cryptocurrency mining network as well as spreading distributed denial-of-service attacks.

The AhnLab Security Emergency Response Center (ASEC) released a report that indicates bad actors are guessing SSH credentials – using dictionary attacks – to install port scanners and malware (such as DDOSbot and CoinMiner).

Once the malicious software is installed, it then scans for other servers to continue the spread. Those same bad actors also can sell the breached IP and account credentials on the dark web.

The attacks are searching for systems with port 22 (the default SSH port) open and then hitting the server with the dictionary attack to install and propagate the malware.

ASEC believes the tools used in the attack were created by the PRG old Team and were modified before being used.

Because this isn't a vulnerability in the SSH software itself, admins and users are warned to ensure passwords are strong and unique, systems are always up-to-date, and (if possible) SSH uses an alternative port (than 22).

This, of course, comes right on the heels of the Terrapin attacks (CVE-2023-48795), which is a prefix truncation attack that targets the SSH protocol.

As far as updates for the Terrapin attacks, the researchers who published the original paper contacted nearly 30 providers of different SSH implementations and indicated it might take some time for all clients and servers to be patched and updated against this attack.


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