The IBM z/VM TCP/IP FOREIGNIPCONLIMIT statement must be properly configured.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-237925	SRG-OS-000142-GPOS-00071	IBMZ-VM-000720	SV-237925r858983_rule	2022-08-31	2

Description
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.

Description

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.

ℹ️ Check
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
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.