The worst I had was the Stoned, and once or twice Michaellangelo virus. The kids would keep bringing it back from school. In those days kids would bring games to school on a floppy and an infection was guaranteed.
I haven't had anything since. Perhaps I'm lucky. Perhaps I'm ignorant. Possibly both.
I haven't had any devastating viruses yet. But within the last 2 months I've received a barrage of them in my email.
I received several like this:
Your parcel has arrived at June 8th, 2014. Courier was unable to deliver the parcel to you.
Print your label and show it in the nearest post office to get a parcel.
Print Shipping Label.
As soon as you click on print label, it launches a virus.
Then I start getting ones saying "Thank you for your purchase." Indicates a receipt is attached.
Open the e:mail and it shows a purchase with a credit card I don't have and an attachment to the e:mail.
The attachment is obviously a virus.
I have run across a few boot sector viruses back in the day. I recall back in 1993 a computer teacher claimed that a disk of mine somehow got the Monkey virus and "cleaned" it with Mcafee AV, which killed the disk in the process. To this day I think it was a false positive, none of my other disks or my home machine was infected. Damn you John Mcafee!
Another boot sector virus I came across in 2003 (!) was the NYB virus. A customer's machine was somehow infected with it, which gave Windows 98SE fits. What tipped me off was the disk I/O was running in MS-DOS compatibility mode. One of the former tech support people must have had it on a disk and it somehow survived into the 2000s!
By far the worst "infection" I encountered recently was that stupid Cryptolocker ransomware. A customer lost some data from it that was thankfully mostly backed up.
On this subject, does anyone know of a pro-active virus detector?. In other words, one that says, "this program is doing something strange and it's not on the list of viruses that I know about.' Most anti-virus programs are just pattern-matchers, which is why the people at Symantec/Norton are saying that they're poised to exit the business.
Right now, it's just plain impossible to anticipate viruses. Someone first has to contract it, an appropriate action taken, then the database and fix have to be distributed. By then, the virus could have infected a billion systems.
In the bad old days, it was pretty simple job to check for boot-sector viruses, but that was long before the distributed-by-i nternet trend started and viruses got more sophisticated.
There are several heuristic plus whitelist programs geared to the enterprise security market. Block all non-authorized software and keep any software that runs from delving into places it shouldn't. The problem with some of these is that any update to software would prevent the software from being used until the whitelist is updated. Might actually be more useful for the vintage software market; all the software is known to be safe for 20 years and modified files can be easily detected.
Malwarebytes collection of tools is pretty good at being proactive, the premium version anyhow is, also Webroot's line is really good at it I've noticed. Stay away from Norton and McAfee nowadays, as they let the most nasty of nasties through. Quite nasty.