Title

The IBM z/VM TCP/IP FOREIGNIPCONLIMIT statement must be properly configured. (Cat II impact)

Discussion

DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. Managing excess capacity ensures that sufficient capacity is available to counter flooding attacks. Employing increased capacity and service redundancy may reduce the susceptibility to some DoS attacks. Managing excess capacity may include, for example, establishing selected usage priorities, quotas, or partitioning. Use the FOREIGNIPCONLIMIT statement to define the maximum number of connections that a foreign IP address is allowed to have open at the same time. If this value would be exceeded, an SSTRESS denial-of-service attack is declared.

Check Content

Examine “TCP/IP” configuration file. If there is no “FOREIGNIPCONLIMIT” statement, this is a finding. If the “FOREIGNIPCONLIMIT” has a value of “0”, this is a finding.

Fix Text

Configure the “FOREIGNIPCONLIMIT” statement with a value specifying the maximum number of connections that a foreign IP address is allowed to have open at the same time. The System administrator should determine the proper value.

Additional Identifiers

Rule ID:

Vulnerability ID: IBMZ-VM-000720

Group Title:

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.