How to find malware backlinks on website

Hello,

Recently I noticed malware backlinks in the footer of my website. I use DLE cms. In a template I do not see any suspicious code. I tried to scan whole website with the "base64" keyword, but also nothing suspicious was found. Maybe can someone give me an idea of how to find such malware backlinks? Maybe is some tool or regex to search suspicious code? Thanks a lot!

it's not important to have a malware in base64 , a simple single line code can also be there for example shell_exec
or many other factors can contribute to it, better check logs