Yahoo users in the US can sign up for Norton security software for a reduced annual subscription of $49.99 (£27), a discount of $20 (£11) on the usual price, after a 30-day free trial.
Yahoo plans to promote the initiative through its network, which includes Yahoo Mail, the Yahoo toolbar and Yahoo search.
In addition, Symantec will provide spyware software for the Yahoo toolbar, and anti-virus and firewall protection for Yahoo broadband users.