SQL Server must limit the number of concurrent sessions for each system account to an organization-defined number of sessions.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-41311	SQL2-00-000100	SV-53793r3_rule		Medium

Description
A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks. For example, boundary protection devices can filter certain types of packets to protect devices on an organization’s internal network from being directly affected by DoS attacks. One way SQL Server can limit exposure to DoS attacks is to restrict the number of connections that can be opened by a single user. SQL Server supports this through the use of logon triggers. When determining the appropriate values for this limit, take the characteristics of the various kinds of user into account, and bear in mind that some applications and some users may need to have multiple sessions open. For example, while a standard account using a simple application may never need more than, say, five connections, a database administrator using SQL Server Management Studio may need significantly more, because each tab in that application counts as a distinct session.

Description

A variety of technologies exist to limit or, in some cases, eliminate the effects of DoS attacks. For example, boundary protection devices can filter certain types of packets to protect devices on an organization’s internal network from being directly affected by DoS attacks. One way SQL Server can limit exposure to DoS attacks is to restrict the number of connections that can be opened by a single user. SQL Server supports this through the use of logon triggers. When determining the appropriate values for this limit, take the characteristics of the various kinds of user into account, and bear in mind that some applications and some users may need to have multiple sessions open. For example, while a standard account using a simple application may never need more than, say, five connections, a database administrator using SQL Server Management Studio may need significantly more, because each tab in that application counts as a distinct session.

STIG	Date
Microsoft SQL Server 2012 Database Instance Security Technical Implementation Guide	2015-03-26

Details

Check Text ( C-47880r3_chk )
Review the system documentation to determine whether any limits have been defined. If not, this is a finding. If one limit has been defined but is not applied to all users, including privileged administrative accounts, this is a finding. If multiple limits have been defined, to accommodate different types of user, verify that together they cover all users. If not, this is a finding. If a mechanism other than a logon trigger is used, verify its correct operation by the appropriate means. If it does not work correctly, this is a finding. Otherwise, determine if a logon trigger exists: EITHER, in SQL Server Management Studio's Object Explorer tree: Expand [SQL Server Instance] >> Security >> Server Objects >> Triggers OR run the query: SELECT * FROM master.sys.server_triggers; If no triggers are listed, this is a finding. If triggers are listed, identify the one(s) limiting the number of concurrent sessions per user. If none are found, this is a finding. If they are present but disabled, this is a finding. Examine the trigger source code for logical correctness and for compliance with the documented limit(s). If errors or variances exist, this is a finding. Verify that the system does execute the trigger(s) each time a user session is established. If it does not operate correctly for all types of user, this is a finding.

Check Text ( C-47880r3_chk )

Review the system documentation to determine whether any limits have been defined. If not, this is a finding.

If one limit has been defined but is not applied to all users, including privileged administrative accounts, this is a finding.

If multiple limits have been defined, to accommodate different types of user, verify that together they cover all users. If not, this is a finding.

If a mechanism other than a logon trigger is used, verify its correct operation by the appropriate means. If it does not work correctly, this is a finding.

Otherwise, determine if a logon trigger exists:

EITHER, in SQL Server Management Studio's Object Explorer tree:
Expand [SQL Server Instance] >> Security >> Server Objects >> Triggers

OR run the query:
SELECT * FROM master.sys.server_triggers;

If no triggers are listed, this is a finding.

If triggers are listed, identify the one(s) limiting the number of concurrent sessions per user. If none are found, this is a finding. If they are present but disabled, this is a finding.

Examine the trigger source code for logical correctness and for compliance with the documented limit(s). If errors or variances exist, this is a finding.

Verify that the system does execute the trigger(s) each time a user session is established. If it does not operate correctly for all types of user, this is a finding.

Fix Text (F-46702r3_fix)
Establish the limit(s) appropriate to the type(s) of user account accessing the SQL Server instance, and record them in the system documentation. Implement one or more logon triggers to enforce the limit(s).