Rule: -- Sid: 2031 -- Summary: The rpc.ypasswd service is used to update user information remotely. This service should not be available outside the local area network, external source. -- Impact: This may be an intelligence gathering activity on available rpc services on a machine connected to external resources. The possibility also exists that an attacker may already have gained access to a NIS server and thus all resources connected to that host. -- Detailed Information: A vulnerability exists in some versions of the rpc.ypasswd service that can lead to a remote root compromise of a vulnerable host. This activity may be an intelligence gathering exercise to ascertain wether or not the host is vulnerable to this attack. This activity may also indicate a possible compromise of a NIS server via a legitimate user account the attacker has previously garnered. Compromise of a master NIS server may present the attacker with easy access to all NIS resources the machine is connected to. -- Affected Systems: All systems running the rpc.ypasswd service. -- Attack Scenarios: The attacker can make a request to update user information via rpc.ypasswd. -- Ease of Attack: Simple -- False Positives: None Known -- False Negatives: None Known -- Corrective Action: Disable the rpc.ypasswd daemon. Disallow all RPC requests from external sources and use a firewall to block access to RPC ports from outside the LAN. -- Contributors: Sourcefire Research Team Brian Caswell <bmc@sourcefire.com> Nigel Houghton <nigel.houghton@sourcefire.com> -- Additional References: SANS: http://www.sans.org/rr/unix/NIS.php http://www.sans.org/rr/unix/sec_solaris.php --
