Question: I have this small virtual server (1GB RAM, 1 vcore), which served me well untill it suddenly started reporting 100% CPU usage because of kswapd0.
Memory consumption is between 50% and 60%.
I've set swappiness to 0 just to check if it releases CPU resources, but it did not.
I've had this issue on 16.04, and now on 18.04 after upgrade.
How to get rid of this kswapd0 CPU hog?

Answer: 
In case someone faces the same issues - the reason was malware: `Multios.Coinminer.Miner`.

`kswapd0` was a binary file located in `/root/.configrc/a/kswapd0`.
What you need to do is:

1. Clear crontab jobs referring to `/root/.configrc`
2. Clear `ssh` keys
3. Delete `/root/.configrc`
**Malware running as guest**

If you have ever enabled Ubuntu's guest account and later enabled SSH, you may have malware running using your guest account.

```
sudo find /home -f kswapd0

```

It can be found in any user's home directory, such as `/home/guest/.configrc/`

Joining any network (conference, cafe, city) that has a compromised machine, or if you use a service like `ngrok`, all while having SSH open on your system leaves your computer exposed to this simple guest vulnerability.

Because privileges were never elevated (guest can't write files outside /home/guest, nor sudo without password), I was able to delete the guest account and everything is running normally.