Rule: -- Sid: 1892 -- Summary: This event is generated when SNMP communications contain a NULL value the authentication string. -- Impact: Medium to Serious. Depending on if the community string was for read-only, read-create or read-write an attacker could gain a varying level of access to a system. -- Detailed Information: An SNMP community string is the authentication process that a host running SNMP uses to grant access. -- Affected Systems: Numerous. Routers, switches, servers, NAS systems, many others. -- Attack Scenarios: An attacker can launch a scan of all network attached devices looking for port 161 (UDP) and then attempt to gain access using SNMP. -- Ease of Attack: Simple. There are many free SNMP "tree walking" programs, an example of such is getIF. -- False Positives: None Known -- False Negatives: None Known -- Corrective Action: Make sure that all devices that have SNMP turned on have complex passwords assigned. Disable unneeded WRITE / CREATE community strings. Since SNMP traffic is not encrypted, use a packet filtering firewall to restrict SNMP communications to the protected network. -- Contributors: Sourcefire Research Team Brian Caswell <bmc@sourcefire.com> Nigel Houghton <nigel.houghton@sourcefire.com> Snort documentation contributed by Mike Rivett ebiz@rivett.org -- Additional References: GetIF: http://www.wtcs.org/snmp4tpc/getif.htm CVE: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-1999-0517 --
