It would seem that a single specially malformed IPv6 packet is enough to completely lock up a PC protected by several versions of Kaspersky Internet Security.  There is currently a private patch available for machines suffering from this issue and there will be an official patch pushed out in the very near future.  According to The Register this flaw was originally reported to Kaspersky in January but as they had not released a patch the original discoverer of the flaw has gone public, which was obviously what it took to get them to fix the issue.  If you run into problematic PCs over the next few days you might want to check for Kaspersky Labs software before you really get into troubleshooting.

"After receiving feedback from the researcher, Kaspersky Lab quickly fixed the error. A private patch is currently available on demand and an autopatch will soon be released to fix the problem automatically on every computer protected by Kaspersky Internet Security 2013."

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