If your site is loading hidden iframes from *.ftp1.biz/pony, look for a curlor file_get_contents call to http://wordpresstest2.info/1.txt.When you visit this site, it generates random iframes:
http://lsghmr.ftp1.biz/pony ( 206.212.240.20)
http://rchscbul.ftp1.biz/pony ( 206.212.240.20)
http://idzui.ftp1.biz/pony
http://vtfptnmxk.ftp1.biz/pony
That are displayed on the compromised sites.