The Iframe Virus, a Headache for Webmasters
The iframe virus is a common virus encountered by many webmasters. The virus inserts an iframe code into the site index without the webmaster's knowledge, even when the computer or FTP program is changed. It can be quite late to understand if the iframe code has infected the page. One way to tell is when clean pages start to give errors. Pages that give variable code errors are often pages infected with the iframe virus.Don't Forget Antivirus on Your Computer
The most accurate solution, assuming it's a computer-related error, is to take all FTP information, delete the iframe codes, and re-upload the site. It is necessary to log into the site again from the server panel (cPanel), change the password, and not check the site via FTP again. When logging in again via FTP, the password is saved, and the iframe codes are placed in the software again. For this reason, installing antivirus on your computer is recommended. 
