Computer viruses and rootckits.

Online virus scaner.
Rootkit checker.
- HijackThis.
- GMER.
Antivirus software.
- Debian.
- Windows.
  - Nod32 removal.

Online virus scaner.

Rootkit checker.

For Debian:

$ sudo apt-get install rkhunter chkrootkit

$ sudo rkhunter -c
...

$ sudo chkrootkit
...

http://www.rootkit.nl/projects/rootkit_hunter.html

For Windows just use Sysinternals suite. There are two tools which help a lot:

procexp.exe to find which process lock file and path to executable images for removing unwanted software.
autoruns.exe to find program and service registration.

Also you may use less powerful but built-in msconfig.exe to investigate startup processes registration.

HijackThis.

Works nice on 32-bit Windows. But fail to properly handle paths on 64-bit.

Autoruns from sysinternals supresses HijackThis by quality and number of detected places.

http://sourceforge.net/projects/hjt/: Home page
https://en.wikipedia.org/wiki/HijackThis: Wiki page.

GMER.

List processes, services, autostarts, scans for rootkits or 3rd party file registration.

Under Windows 10 x64 it cause reboot due to write to rean-only memory.

http://www.gmer.net/: Home page.
https://en.wikipedia.org/wiki/GMER: Wiki page.

Antivirus software.

Debian.

ClamAV - anti-virus utility for Unix:

$ sudo apt-get install clamav

Windows.

Free active antivirus:

Windows Defender
Avast - free Antivirus is free only for personal and non-commercial use.

Free one time scan antivirus:

Nod32 removal.

Disable nod32 services by 'msconfig' utility.

Remove such keys from registry by 'regedit':

HKEY_LOCAL_MACHINE\SOFTWARE\ESET
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Enum\Root\LEGACY_NOD32DRV
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\eamon  ==>
              ... easdrv easdrv EhttpSrv ekrn epfw Epfwndis epfwtdi