Malicious Code in my website JTS-post Assistant Output

[arefrasool2004]

Joomla! Version: Joomla! 1.5.23 Stable [ senu takaa ama baji ] 04-March-2011 18:00 GMT
configuration.php: Writable (Mode: 755 ) | Architecture/Platform: Linux 2.6.18-374.3.1.el5.lve0.8.44PAE ( i686) | Web Server: Apache ( http://www.goldenpeacockawards.com ) | PHP Version: 5.2.13
PHP Requirements: register_globals: Disabled | magic_quotes_gpc: Enabled | safe_mode: Disabled | MySQL Support: Yes | XML Support: Yes | zlib Support: Yes
mbstring Support (1.5 or above): Yes | iconv Support (1.5 or above): Yes | save.session_path: Writable | Max.Execution Time: 30 seconds | File Uploads: Enabled
MySQL Version: 5.0.92-community-log ( Localhost via UNIX socket )

SEF: Disabled (without ReWrite) | Legacy Mode: Disabled | FTP Layer: Disabled | htaccess: Implemented
PHP/suExec: User and Web Server accounts are the same. (PHP/suExec probably installed)
PHP Environment: API: cgi | MySQLi: Yes | Max. Memory: 256M | Max. Upload Size: 2M | Max. Post Size: 8M | Max. Input Time: 60 | Zend Version: 2.2.0
Disabled Functions:
MySQL Client: 5.0.92 ( latin1 )

[arefrasool2004]

I have checked .htaccess and also the content of the website there is nothing suspicious only when i check the cache of the webpages it shows malicious content.

[mandville]

your joomla is out of date, run through checklist 7 safe route to recovery

[ ] Run the Forum Post Assistant / FPA Instructions available here and are also included in the download package.

[ ] Ensure you have the latest version of Joomla. Delete all files in your Joomla installation. Replace the deleted files with fresh copies of a current full version of Joomla, and fresh copies of extensions and templates used. Only by replacing all files in the installation (including extensions and templates) can you be sure to remove the backdoors inserted and hidden in files and directories

[ ] Review Vulnerable Extensions List

[ ] Review and action Security Checklist checklist 7 to make sure you've gone through all of the steps.

[ ] Scan all machines with FTP, Joomla super admin, and Joomla admin access for malware, virus, trojans, spyware, etc.

[ ] Change all passwords and if possible user names for the website host control panel and your Joomla site.

[ ] Use proper permissions on files and directories. They should never be 777, but ideal is 644 and 755

[ ] Check your htaccess for for any odd code (i.e. code which is not in the standard htaccess supplied as part of the Joomla installation).

[ ] Check the crontab or Task Scheduler for unexpected jobs/tasks.

[ ] Ensure you do not have anonymous ftp enabled