Hi pilletch,
According to information I found on the Web on Lineage, it doesn’t infect all .exe files on a computer in the way you describe.
Have you tried running a boot time scan with avast!?
Right click on the scanner screen and select ‘schedule a boot time scan.’
Reboot as requested.
You will see a blue screen during the scan.
It may be that during this scan, only the malware file itself will be detected, in which case, you can select the option to move the malware to the chest.
If the malware really is infecting .exe files, and you start getting a lot of detections, you can try the repair option.
There’s an example of the scanner screen here:
http://bcheck.scanit.be/bcheck/hj-images/avast-scan.png
