It sounds more like a virus, trojan, or worm. They are malicious, and alter programs without any warning.

I would suggest you update and run your anti- virus software now if not sooner along with any spy-ware and adware programs you may have.

If you think your anti-virus software has been compromised, you can get a free virus-scan from this link. http://security.symantec.com/sscv6/d...d=ie&venid=sym