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RealTime IT News

CERT Warns of Flaw in Popular Network Protocol

The protocol used by the majority of Internet networks around the world is at risk from a new vulnerability discovered by the Oulu University Secure Programming Group (OUSPG) in Finland recently.

The Computer Emergency Response Team Coordination Center (CERT/CC) issued an advisory to all network administrators of a flaw in the simple network management protocol (SNMP), the protocol used to remotely administer routers, switches and network management systems.

The culprit responsible for the security breach seems to be one that underlies most vulnerabilities: buffer overflow and format string errors.

Ian Finlay, CERT/CC Internet security analyst, said vendors were contacted last year about the vulnerability, giving them a chance to create a security patch to address the problem before the rest of the world (notably hackers) found out. All told, more than 240 vendors were contacted after the Oulu group ran a test program on networks that use SNMP as its protocol.

The problem is especially vexing because the problem can't be pinned down to one specific vendor, as is often the case with security vulnerabilities, but must be corrected by many vendors.

If software vendors don't get patches to their customers, CERT/CC predicts "large-scale outages of these devices (that) could disable significant portions of the global network."

The biggest problem with patches, Finlay said, doesn't reside with vendors getting them published and out to their custmers. It's getting system administrators to deploy those patches across their networks.

"As we've seen in the past, getting administrators to actually deploy the patch is the other half of the (problem)," Finlay said. "We haven't seen any (breaches) yet, but we would expect because SNMP is so common and so pervasively deployed that we may see that shortly."

Vendors with vulnerable systems follow: Nokia, Lucent Technologies, Caldera, Hewlett-Packard, Multinet, Lotus, Juniper Networks, 3Com, Novell, Cisco Systems, Microsoft Corp., NET-SNMP, Lantronix, Novell, Marconi, Computer Associates, Red Hat Linux, AdventNet, COMTEK Services Inc., Innerdive Solutions LLC, CacheFlow Inc., Hirschmann Electronics GmbH & Co., FreeBSD, SNMP Research, Redback Networks Inc., and Netscape Communications Corp.

This represents only a partial list of all vendors using SNMP, it's unclear whether others may be affected. CERT/CC recommends administrators visit their Web page of companies that are possibly affected by the vulnerability.

A Web page with security patches, by vendor, is available here. Many listed in the previous paragraph already have patches available or have release dates scheduled.

The organization reported increased information about the SNMP vulnerability making its way through the hacker community, so it's likely only a matter of time before an enterprising cracker creates a distributed denial of service (DDoS) to bring a network to its knees.

The breach is such that it can also let hackers create a "back door" to devices using SNMP, giving hackers the leisure of breaking into the network and returning at a more leisurely pace later.

Security experts warn that disabling SNMP as a defensive measure, which would give administrators time to install a patch, is not an option for many corporations around the world who conduct e-business, since billing functions and ordering will be interrupted.

CERT/CC instead recommends the temporary stopgap of ingress filtering to prevent outside machines from logging into corporate servers. The organization recommends filtering ports 161/udp and 162/udp.

If the two measures above aren't feasible, CERT/CC also suggests restricting SNMP traffic to virtual private networks (VPNs) or to separate, isolated management networks not available to the public.

SNMP 1 has been around since the early 1980s and several efforts have been made to update the standard to SNMP 2 on a global basis, with no success. Though there are some networks using SNMP 2 and SNMP 3, and some networks have switched their remote administration protocol to remote monitoring (RMON - which tells technicians more than whether the equipment is functioning or not), most still use SNMP 1.

Finlay suspects the nature of the vulnerability doesn't make versions two or three any more secure than SNMP 1.