GEN:SID 1:2152
Message WEB-PHP test.php access
Summary This event is generated when an attempt is made to access a script not normally used in a production environment.
Impact Information gathering.
Detailed Information This event indicates that an attempt has been made to access a test script (test.php) that would not normally be used in a production environment.

The attacker may be trying to gain information on the php implementation on the host, this may be the prelude to an attack against that host using that information.

In applications such as Horde or IMP, the test.php script may reveal valuable server information to the attacker.
Affected Systems Any host using php applications such as Horde or IMP.

Other php applications may use a file named test.php also.
Attack Scenarios An attacker can retrieve a sensitive file containing information on the php application on the host. The attacker might then gain administrator access to the site or database.
Ease of Attack Simple.
Corrective Action Check the php implementation on the host. Ensure all measures have been taken to deny access to sensitive files.

Check the host for signs of compromise.
Additional References  
Rule References nessus: 11617