PwnRig

What it is

PwnRig is a cryptocurrency miner, a modified build of the XMRig mining program, used by the group researchers call the 8220 Gang. It arrives with a loader script and a bot controlled over a chat channel, based on Tsunami. Security monitoring of this group's attacks flagged changes to /etc/ld.so.preload more than once; that file makes a library load into every program, a common way to hide things. No report describes that library, so we can't say exactly what it hides, and we advise rebuilding to be safe rather than trusting the server to check itself.

How it gets in

Through internet-facing services that are unpatched or badly set up, such as Redis, Apache and Oracle WebLogic.

Close the door: Patch and restrict public access to exposed services such as Redis, Apache and WebLogic, and do not expose management ports to the internet. Monitor for cron modification, execution from /tmp and writes to /etc/ld.so.preload, which the cited Falco coverage flags.

How to tell if you have it

Signs published for this threat. One sign alone proves little: names get reused, and newer versions change them. Look for several together.

These commands only look. They change nothing.

Look for the known file locations

sudo ls -la /tmp/.python 2>/dev/null

Search for the known file names (slow on big disks)

sudo find / -xdev \( -name 'xms' -o -name 'pwnrig' -o -name 'initdr' -o -name 'sysdown' -o -name '.ntpdate' -o -name '.tmpest' \) 2>/dev/null

Look for the known process names, and where each one runs from

for p in $(pgrep -f 'dbused'); do echo "$p $(sudo readlink /proc/$p/exe)"; done

List running programs that live in a temporary folder (real software almost never does)

sudo ls -l /proc/[0-9]*/exe 2>/dev/null | grep -E '/(tmp|var/tmp|dev/shm)/'

Fingerprint a suspect file and compare it with the list below

sudo sha256sum /path/to/suspect-file

Known file fingerprints (SHA-256). A match identifies that exact file; newer builds differ.

How sure these signs are: We advise rebuilding as a precaution: reports flag /etc/ld.so.preload being changed but don't describe what was hidden, so a check run on the infected server may miss things, and finding nothing does not prove it is clean. The attackers choose their own file and process names. dbused looks like the real dbus service and Java (Update) looks like a real updater, so check where the process runs from. .ntpdate imitates a time tool. xms, initdr and .tmpest are weak signs alone: they are short or shared names, and researchers saw the same name with different fingerprints, or the same fingerprint under another name. /tmp/.python belongs to the companion bot, not the miner. One report carries no date (likely 2021); the other is from 2023.

How to deal with it

Removing it in place isn't safe. Here is what to do instead, in order:

1. Don't try to clean it in place. Plan to rebuild the server from a fresh install.
2. Cut the server off from the internet, but keep a way to log in, such as your hosting provider's web console. Save evidence: your scheduled tasks, init.d scripts and services, /etc/ld.so.preload, the contents of /tmp, and the SHA-256 fingerprint of each suspect file. If you can, collect them from a rescue disk.
3. Copy off your data: databases, website files and documents. Don't copy programs, scripts, scheduled tasks, init.d entries or /etc/ld.so.preload; any of those could bring it back.
4. Reinstall from a fresh image, install all updates, then restore only the data you copied and checked.
5. From a clean computer, change every password, key and token that was on the server, including SSH private keys and cloud keys, and cancel the old ones. The loader looks for private keys on the server.
6. Before you reconnect, patch the service that was exposed, such as Redis, Apache or WebLogic, and make sure it can't be reached from the internet without a login. Don't leave management ports open to the internet. Keep watching for changes to scheduled tasks, programs running from /tmp and changes to /etc/ld.so.preload.

What Minaki Scan does about it

Related threats

Sources

This page is written by MinakiLabs in our own words. The facts above come from this published research; credit and thanks to its authors.

• SP 800-83 Rev. 1, Guide to Malware Incident Prevention and Handling for Desktops and Laptops, NIST (2013-07)
• 8220 Gang Continues to Evolve With Each New Campaign, Sysdig (2023-02-14)
• 8220 Gangs Recent use of Custom Miner and Botnet, Fortinet (FortiCNAPP, formerly Lacework Labs)