Software that can help Web sites neutralize the sort of denial of service attacks that felled Yahoo and others in recent days has been posted by the FBI and computer service organizations.

The FBI and security site Packet Storm have posted software that can detect whether a site is being attacked. Once an attack is identified, Web site managers can implement plans to deflect the crippling amount of traffic generated by the assault. Several distributed denial of service (DDoS) attacks this week left Web surfers unable to access sites including Yahoo, eBay, E*Trade, Buy.com, Amazon.com and others. The FBI has pledged to track down the parties who have been performing the attacks. DDoS programs such as Trinoo, Tribe Flood Network (TFN) and Stacheldraht enable an attacker to use other people_s computers to overwhelm a target with packets of information sent over the Internet. The packets typically are constructed to take up an inordinate amount of the target computer_s attention.