Question about possible malware

I’ve been watching my 404 errors in Awstats and I’ve noticed that both “/wp-content/uploads/_input__test.php5” and “/wp-content/uploads/_input__test.php.” are returning a 404 once or twice daily. I researched and found these two files are associated with malware. I’ve searched my database and directories and can find no instance of these 2 files. I’m wondering if anyone could tell me what might be creating these 404s and should I be concerned?