The intrusion prevention capabilities of Cisco Systems' routers could be prone to attack, after the networking giant revealed two vulnerabilities in its key operating system. The vulnerabilities affect those versions of Cisco's Internetwork Operating System (IOS) that start with "12.3" and "12.4". Almost all Cisco routers run a version of IOS. The flaws allow a hacker to circumvent the IPS protection built into the affected routers and also cause routers to crash.