Necurs Botnet malspam pushes Locky using DDE attack

Necurs Botnet malspam pushes Locky using DDE attack
Introduction I've seen Twitter traffic today about malspam from the Necurs Botnet pushing Locky ransomware using Word documents as their attachments. These Word documents use the DDE attack technique, something I already wrote about in a previous diary covering Hancitor malspam on 2017-10-16. Here's a link to My Online Security's writeup about today's malspam from the Necurs Botnet. I opened one of the Word documents in my lab environment and found a 1st stage malware (presumably a downloader) and a 2nd stage malware (Locky) during the infection. Today's diary reviews the traffic and malware. Shown above: Flow chart for the infection process. Emails Below is a copy from one of the emails. If found several dozen of them; however, I only noticed 3 distinct Word documents from the attachments. Shown above: Screen shot from one of the emails. Attachments The email attachments exhibited characteristics similar to previous Word documents using the DDE attack method. Shown above: Opening the Word document in a test environment (1 of 3). Shown above: Opening the Word document in a test environment (2 of 3). Shown above: Opening the Word document in a test environment (3 of 3). Network traffic Traffic was a bit different than I've seen with recent attachments from the Necurs Botnet. The first HTTP request returned a base64 string that contained further URLs for the 1st-stage malware download. The second HTTP request returned the 1st-stage malware. Two follow-up HTTP POST requests came from the 1st-stage malware with the User-Agent string Windows-Update-Agent. Then came an HTTP POST request that returned the Locky ransomware binary. The Locky binary was encoded as it passed through the network, and it was decrypted on the local host. No callback traffic from the Locky binary was noted. I just saw some more HTTP POST requests from the 1st-stage malware. Shown above: Traffic from the infection filtered in Wireshark. Shown above: First HTTP request returned a base64 string. Shown above: 1st-stage malware downloaded. Shown above: 1st-stage malware possible connectivity check. Shown above: 1st-stage malware callback traffic to a probable command & control server. Shown above: Locky binary sent to the infected Windows host. The infected Windows host The infected host exhibited characteristics of a Locky ransomware infection. The Locky binary deleted itself after the infection. However, the 1st-stage malware was made persistent on the infected host, and I saw an update in the Windows registry for it. Shown above: Desktop of an infected Windows host. Shown above: Locky ransom cost was .25 bitcoin. Shown above: 1st-stage malware persistent on my infected host. Indicators Traffic from my infected windows host: 66.36.173.246 port 80 - ryanbaptistchurch.com - GET /KJHDhbje71 62.212.154.98 port 80 - *shamanic-extracts.biz* - GET /eurgf837or *ds.download.windowsupdate.com* - POST / 77.123.53.200 port 80 - *gdiscoun.org* - POST / 180.222.185.74 port 80 - hair-select.jp - POST /fef44gddd.enc 77.123.53.200 port 80 - gdiscoun.org - POST / 77.123.53.200 port 80 - gdiscoun.org - POST / *www.bing.com* - GET /favicon.ico Other URLs from the infected host: 84.234.64.216 port 80 - *arkberg-design.fi* - GET /KJHDhbje71 98.124.251.65 port 80 - alexandradickman.com - GET /KJHDhbje71 68.171.62.42 port 80 - centralbaptistchurchnj.org - GET /eurgf837or 175.107.146.17 port 80 - conxibit.com - GET /eurgf837or Malspam attachments: SHA256 hash: 3fa85101873d1c3447594c309ea1e324beb578843e1fab7c05189830d2def126 File size: 13,345 bytes File name: i_[six random digits].doc File description: attachment from the malspam SHA256 hash: ea132c34ebbc591eda78531e2bfb9a4cb40e55a245191f54e82df25be9b58db2 File size: 13,341 bytes File name: i_[six random digits].doc File description: attachment from the malspam SHA256 hash: 4a7f805f6b8fec64d3cf07c02a1d200c703ce4cc6ddf2dabd56ad9d6c936c603 File size: 13,344 bytes File name: i_[six random digits].doc File description: attachment from the malspam Malware from the infected Windows host: SHA256 hash: d2cca5f6109ec060596d7ea29a13328bd0133ced126ab70974936521db64b4f4 File size: 116,482 bytes Initial location: C:\Users\[username]\AppData\Local\Temp\rekakva32.exe Persistent location: C:\Users\[username]\AppData\Local\Temp\{b291bae7-2824-ea5c-c352-94c8757176af}\a3W22f79.exe File description: First-stage malware (checks in to C2 server/downloads Locky binary) Registry update: KHCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run SHA256 hash: 4c054127056fb400acbab7825aa2754942121e6c49b0f82ae20e65422abdee4f File size: 651,264 bytes File location: C:\Users\[username]\AppData\Local\Temp\a3W22f79.exe File description: Second-stage malware, Locky ransomware Final words Standard disclaimer: As always, it's relatively easy to follow best security practices on your Windows computer. Software Restriction Policies (SRP) or AppLocker can easily prevent these types of malspam-based infections from occurring. This is an interesting development, because it shows how the DDE attack technique has spread to large-scale distribution campaigns. It's not new, and I'm not sure how effective it really is. If you know of anyone who was infected from one of these DDE-based Office documents, please tell your story in the comments. Pcap and malware samples for this diary can be found here. --- Brad Duncan brad [at] malware-traffic-analysis.net	Brad 377 Posts ISC Handler Oct 19th 2017
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