Mindful of looming competition from Microsoft ( MSFT), Symantec ( SYMC) is pairing up with Yahoo! ( YHOO) to bring its Norton Internet Security product to Yahoo! users. Beginning Tuesday, Yahoo! will offer its customers a 30-day trial of the security software package. When it expires, Yahoo! users can purchase a yearlong subscription to Norton Internet Security for $49.99, a special promotional fee. The suite normally sells for $69.99. Norton Internet Security includes Norton AntiVirus software and Norton Personal Firewall. The all-in-one product filters spam, scans email and instant messages to remove viruses and worms, detects spyware and blocks identity thieves, Symantec said. The co-branded product is available as a download and will be marketed across the Yahoo! network, including its search, mail and toolbar properties. Yahoo! said the deal will bring a "comfortable security blanket" to its users. "Simple, dependable Internet security solutions help give people peace of mind" when using the Internet. In recent trading, Symantec shares dipped 1.3%, or 20 cents, to $15.40. Yahoo! was off 0.7%, or 19 cents, to $26.75. Symantec reports its quarterly earnings on Wednesday.