If attackers compromise your site, they might insert malicious code that redirects visitors to phising or malware sites. Or they might also lure visitors to the malicious redirects with spam email. Those messages can be something as simple as:
If you see messages like this about your own site, you should review your website content for files containing malicious redirects. Typically, these files are created in separate directories, like these:
These files will contain a list of domains and a line of code that performs the actual redirect — they look something like this:
<meta http-equiv="refresh" content="2; url= ">
http-equiv gets the visitors' browser to load the malicious website.
Obviously, you want to remove any files containing redirects as soon as possible.
There are many ways attackers can insert this malicious code on your site. If this has happened to you, we recommend the following to secure your site:
You can also find more information about application security compromises in My website was hacked. What should I do?.