The threats are serious however, and apply to router vulnerabilities in public sector and private networks. The first weakness applies to applications using the TCP Internet protocol and affects router systems of any kind; the second refers to a weakness in the border gateway protocol (BGP) of Cisco Systems' Internetwork Operating System (IOS) SNMP Service.

"The TCP vulnerability can interrupt services on the router or other TCP devices," said Shawn Hernan an expert with CERT. "SNMP vulnerability can actually crash the router, [but] in most cases the router will automatically reload in response to a SNMP attack." It appears to be coincidental that both vulnerabilities were announced at the same time.

Officials say they have yet to see any attempt by hackers to exploit the weaknesses, but allowed that the scale of the problem is large. The BGP problem affects a wide variety of Cisco routers and switches, and someone "with modest skills" can attack the vulnerability and crash the router, Hernan says. Also the number of workarounds used by network administrators mean some critical services for security may have been turned off. They warned that best practices alone may not be sufficient to ward off the threat.

DHS and CERT spokesmen praised Cisco, which discovered the problem, for proactively informing CERT and addressing the vulnerability. Cisco has posted security updates and patches on its website. CERT has issued its own technical alert on the problem.