There's a very critical vulnerability going around that has installed backdoors on SSH servers.
If you have servers or systems on Linux, check if you're affected by running the command:
```$ hexdump -ve '1/1 "%.2x"' "/lib/x86_64-linux-gnu/liblzma.so.5" | grep -q f30f1efa554889f54c89ce5389fb81e7000000804883ec28488954241848894c2410```
(extracted from `detect.sh` provided by Andres Freund)
Kali and Fedora are generally affected. Debian and Ubuntu seem to be vulnerable only if dev/test repositories have been enabled.
More info here:
https://boehs.org/node/everything-i-know-about-the-xz-backdoor