PHP.Pirus

SUMMARY

PHP.Pirus is the first virus written in PHP, a server-side scripting language used for dynamic Web page generation. The virus runs only on servers with PHP interpreters. This virus cannot be contracted by simply visiting an infected Web page. The virus is saved as a file on the hard drive, and it inserts code into .php and .htm files to call itself. The name of the virus file varies, but is likely to use the extension .php

Protection

• Virus Definitions (Intelligent Updater) November 13, 2000

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

This virus is written in PHP and is contained in a file that is 718 bytes long. When executed, the virus searches the current directory for files with .php or .htm extensions. If one of these files is writable, the virus opens the file to determine if the file is already infected. If the file is not infected, the virus inserts a line to execute the original viral file rather than appending itself to the infected file.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

To remove the virus:

1. Delete the original virus file.
2. Examine each .php, .htm, or .html file to determine whether it contains virus code, and then edit these files to remove the code.

For example, if the virus file is named Virus.php, delete the file Virus.php and remove the following virus code from all php, .htm, or .htm files that have the code:

<php
include "virus.php"
/php>