Malware spam: "Per E-Mail senden: DOC0000329040"

This German-language spam comes with a malicious attachment. It appears to come from the victim themselves, but this is just a simple forgery.

From:    victim@victimdomain.tld
Date:    17 May 2016 at 13:28
Subject:    Per E-Mail senden: DOC0000329040

Folgende Dateien oder Links können jetzt als Anlage mit Ihrer Nachricht
gesendet werden:

DOC0000329040

Attached is a ZIP file that matches the reference number in the subject and body text. I have only seen one sample, downloading a binary from:

katyco.net/0uh8nb7

The VirusTotal detection rate is 4/57, the comments in that report indicate that this is Locky ransomware and the C&C servers are at:

188.127.231.124 (SmartApe, Russia)
176.53.21.105 (Radore Veri Merkezi Hizmetleri, Turkey)
217.12.199.151 (ITL, Ukraine)
107.181.174.15 (Total Server Solutions, US)

Recommended blocklist:
188.127.231.124
176.53.21.105
217.12.199.151
107.181.174.15