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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-237925	IBMZ-VM-000720	SV-237925r649615_rule		Medium

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.

STIG	Date
IBM zVM Using CA VM:Secure Security Technical Implementation Guide	2021-06-16

Details

Check Text ( C-41135r649613_chk )
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 (F-41094r649614_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.