Virus ignored, then picked up

[chester49]

Hello group,

I recently got an e-mail with suspicious compressed attachment. Put attachment on my desktop and scanned it with Avast 4.8. No reaction from Avast, just a lightning-quick scan and then nothing. But when I ran my weekly Avast sweep of my hard drive, Avast identified the still-compressed and unopened attachment (now in recycle bin) as a virus, calling it Win32: Autorun - APG [WRM]. Anybody know why Avast failed to identify it on the individual scan, then picked it up on the hard-drive sweep?

thanx,
Chet

[alanrf]

All I can imagine is that an avast update came in between your scanning your desktop attachment and your weekly scan. 

The same avast database is used for both scans so something had to change between the two scans.

It would require the resources of the avast team to drill down and check the dates and times of both versus the database updates.

Tough one to call - what is a better use of the avast team's time - to investigate your now historic event or devote their efforts to current information and keeping the database up to date to protect us all? 

 

[Lisandro]

Maybe the signature was added in between.
Maybe your first scanning wasn't enough deep. Did you right click the file and scan it?

[chester49]

Yes, first scan way by right-clicking on the compressed file. And there were several updates between the two scans. That could've been it, I guess.

thanx,
Chet

[Lisandro]

Yes, first scan way by right-clicking on the compressed file.

The most thorough scanning available.

And there were several updates between the two scans. That could've been it, I guess.

Most probably.