Sites got Hacked. Need the FIX & Security - PHP/MySQL

My sites were getting hacked about 2 days ago using an iframe code that went to a .cn site and apparently downloaded a trojan to the users machine. Well i cleaned up all my sites as it infected php, coldfusion, html files all the same with this little line of code on the end of each page. I changed all my passwords to ones using letters, numbers, symbols etc to avoid possible cracking. The code was and still is: < iframe src="[login to view URL] width=1 height=1 style="visibility: hidden">< / iframe > (spaced out to avoid a problem here) Now two months later it's back, same issue, downloading a trojan to users machine. I am deleting the two sites that are having this issue at present only these two are more due to this obvious exploit. Looking for experts who can fix the problem ASAP. Sites we have issues are - [login to view URL] etc