Malicious File Waring

I have the following warning from Wordfence;

File appears to be malicious: wp-content/cache/object/201/00a/20100a430fed5771552ee479c00eb317.php

This file appears to be installed by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans. The text we found in this file that matches a known malicious file is: “eval”;a:2:{i:0;s:5:”EAPLq”;i:1;s:35:”/[^a-z\/'”]eval\([^\)]+[‘”\s\);]+/i”;}s:15:”preg_replace /e”;a:2:{i:0;s:5:”G85F2″;i:1;s:47:”/preg_replace\s*\(.+[\/\#\|][i]*e[i]*[‘”].+\)/i”;}s:9:”auth_pass”;a:2:{…”. The infection type is: Suspicious eval with base64 decode..

I have deleted this file (and one very similar that appears with it) but they keep returning.
Any thoughts?

Thanks
Phil