"Insecure Internet activity. Threat of virus attack" is a fake warning alert that appears as an interstitial ad page. "Insecure Internet activity. Threat of virus attack" alert was disened by Trojan Zlob creators. They are showing this type of message usually after fake video codecs instalation. If user clicks on "Insecure Internet activity. Threat of virus attack" fake warning message, hi will be directed to a rogue antispyware promoting websites. Thise websites will try to trick user into purchasing the "full" version of a rogue anti-spyware program that they are promoting. "Insecure Internet activity. Threat of virus attack" messages looks like this:

"Reported Insecure Browsing: Navigation blocked.
Insecure Internet activity. Threat of virus attack
Due to insecure Internet browsing your PC can easily get infected with viruses, worms and trojans without your knowledge, and that can lead to system slowdown, freezes and crashes.
Also insecure Internet activity can result in revealing your personal information.
To get full advanced real-time protection for PC and Internet activity, register WinSpywareProtect.
We recommend you to protect your PC now and continue safe Internet browsing.
Click here to get full advanced real-time protection and continue browsing.
Continue to this website unprotected (not recommended)."

So "Insecure Internet activity. Threat of virus attack" fake message is designed to trick user into buying rogue anti-spyware programs like WinSpywareProtect and Antivirus 2008.
Delete "Insecure Internet activity. Threat of virus attack" as soon as possible!