LFD log line

Hi, I encounter a massive BruteForce Attack on IMAP services on my server. I notice a lot of lines like these ones in my /var/log/lfd.log : Jan 17 13:01:09 cloud lfd[17320]: here: [method=PLAIN, ] [] Jan 17 13:01:09 cloud lfd[17320]: here: [method=PLAIN, ] [] Can someone explain me what it means. Particularly, what means the "here" ? I searched the whole web and didn't find any clue ... Thank you for your help.