Avast Virus Definitions decreasing

Viruses and worms
1

Hi, I’m new here. I used to be an avid supporter of AVG for many years, then it became too bloated, and I was forced to use an Australian version which had all sorts of site-bocking code. Nothing would work. So I switched to Avast Free, and absolutely love it! The Boot scan works beautifully, and it’s a fantastic feature. Avast detected several worms and trojans missed by AVG - especially malicious “drive by” downloads from websites.

However, during the last week or so, I’ve noticed that every time I do a definitions update, they keep decreasing! Last week the number of definitions was nearly 3 million, not it’s down to 2,294,692! Before the latest update to 100910-0 there wre something like 2,333,000 definitions.
Is this due to the fact that older virus definitions are being dropped and false positives removed from the database? Or is this related to the license I have with the free version? I’m worried that with the reduced number of definitions after each update, a virus or trojan might “slip through” the scanning process or be missed by the resident shield. I’m using Avast Free Edition 5.o.667,Win XP SP3. I also have Spyware Blaster 4.4, Zone Alarm 9.2.057.000 and Ad Aware 8.3.2 with System Restore turned off. I also wipe the Windows prefetch case on a regular basis as well as deleting TMP files. Hopefully there’s a simple explanation and a virus isn’t wiping the Avast database clean.

2

http://blog.avast.com/2010/09/06/spring-cleaning-in-our-virus-database/

3
I also have Spyware Blaster 4.4, Zone Alarm 9.2.057.000 and Ad Aware 8.3.2
I absolutely recomend you dropp ad-aware and replace it with Malwarebytes Anti-Malware 1.46 http://filehippo.com/download_malwarebytes_anti_malware/ bc it is the #1 malware remover
4

Thasnk you Altarir for directing me to the “spring cleaning” post on the blog and the simple explanation. Also, thank you Pondus for recommending a better replacement for Ad-Aaware. Like AVG, I was using it for years, but seeing as Anti-Malware is a better defence, I’ll be downloading it immediately. Once again, thanks to the both of you.