Wandering Thoughts archives


Looking at how many viruses we've seen in email recently

Once upon a time people were very worried about viruses being spread through email and devoted a lot of time and effort to eradicating them (sometimes going so far as to refuse all zipfiles and the like). The last time I looked at this we had very few viruses being recognized, but that was a couple of years ago and today I was curious to see if things had changed.

(Technically what I am actually looking at is the amount of detected malware. Viruses are only one of the types of malware that can be spread through email.)

Because our email system does two stages of filtering I have to give two sets of numbers. All of these are over the last 30 days because I decided that that was a good time range for 'current activity'. First, in our SMTP-time milter based filtering, which only covers some email, we checked 44,000 messages and found 316 'viruses'. This is actually highly misleading because our commercial black box spam+AV filter classifies some phish messages as viruses instead of plain spam. It turns out that most of the detected viruses were in fact phishing messages; 232 out of 318, leaving 84 real viruses.

The main anti-spam processing (which every accepted email goes through) handled 503,000 messages and found 2,445 viruses. Again this includes some phishing messages but this time a lot fewer, only 913. That leaves 1,532 real viruses or a detected virus rate of 0.3% of our incoming email.

Actual malware is potentially very damaging, so I'm glad we have the anti-virus filtering even if we don't see many of them. I might feel differently if we paid any significant amount of money for it (although there are free options if we ever need them).

(I was going to say something about classifying phish spam as malware but my thoughts on this are long enough that I want to put them in a separate entry.)

spam/EmailVirusCount-2013-08 written at 00:16:08; Add Comment

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