Hello.  The malicious code came from the plugin 'metatags'.  I´ve merged some codes to add the function to 'access_privacity plugin'.
 
Sorry for this mistake.  My site gone down like yours ( www.assetans.org.br ).

Only a few minutes ago I changed the name of the directory "access_privacity" and run the 'upgrade.php' to solve the problem.
 
I´ll fix it, make it work in 1.7.10 and be more carefull.
 
Renato

 @Tarciso Vieira de Melo - please, run the 'úpgrade.php' to refresh your cash after change the name of the directory (or deleted).

Thanks a lot to the community!!!!! Deleting the folder  access_privacity solved the problem. My social Network Site for my school is back again. I am very released that it is no security problem.

Thanks for all help and tipps!