An adversary scans for RPC services listing on a Unix/Linux host. This type of scan can be obtained via native operating system utilities or via port scanners like nmap. When performed by a scanner, an RPC datagram is sent to a list of UDP ports and the response is recorded. Particular types of responses can be indicative of well-known RPC services running on a UDP port. Direct RPC scans that bypass portmapper/sunrpc are typically slow compare to other scan types, are easily detected by IPS/IDS systems, and can only detect open ports when an RPC service responds. ICMP diagnostic message responses can help identify closed ports, however filtered and unfiltered ports cannot be identified through TCP RPC scans. There are two general approaches to RPC scanning: One is to use a native operating system utility, or script, to query the portmapper/rpcbind application running on port 111. Portmapper will return a list of registered RPC services. Alternately, one can use a port scanner or script to scan for RPC services directly. Discovering RPC services gives the attacker potential targets to attack, as some RPC services are insecure by default.
The table(s) below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Relevant to the view "Mechanisms of Attack" (CAPEC-1000)
Standard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.
RPC scanning requires no special privileges when it is performed via a native system utility.
The ability to craft custom RPC datagrams for use during network reconnaissance via native OS utilities or a port scanning tool. By tailoring the bytes injected one can scan for specific RPC-registered services. Depending upon the method used it may be necessary to sniff the network in order to see the response.
The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Bypass Protection Mechanism
Typically, an IDS/IPS system is very effective against this type of attack.
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Page Last Updated or Reviewed:
July 31, 2018
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