Although the number of zombie computers able to launch network attacks is growing, and the size of network attacks is outstripping the growth of networks, ISPs are still generally optimistic about their ability to address security issues, a recent study of ISPs by Arbor Networks indicates.

That's because providers have invested “hundreds of millions of dollars in their backbone and security infrastructure,” Arbor reported. “Over half of the surveyed providers now believe ISPs can effectively mitigate most Internet attacks against their backbone infrastructure and customers. In the arms race between ISPs and hackers, ISPs believe they are ahead.”

Many ISPs are using managed security services to detect and disarm distributed denial of service (DDoS) attacks. Voice-over-IP services are still vulnerable, however, and most ISPs admit they can't protect against very large DDOS attacks.