Threat Level: green Handler on Duty: Xavier Mertens

SANS ISC: SANS Internet Storm Center SANS Internet Storm Center

Sign Up for Free!   Forgot Password?
Log In or Sign Up for Free!

Latest Diaries

The Importance of Out-of-Band Networks

Published: 2021-12-06
Last Updated: 2021-12-06 13:14:53 UTC
by Xavier Mertens (Version: 1)
0 comment(s)

Out-of-band (or "OoB") networks are usually dedicated to management tasks. Many security appliances and servers have dedicated management interfaces that are used to set up, control, and monitor the device. A best practice is to connect those management interfaces to a dedicated network that is not directly connected to the network used to carry applications/users' data. If a physically separated network is always best, a dedicated VLAN could do the job in most cases (if properly configured). What we typically find on OoB networks are:

  • Network devices (switches, routers, access-points)
  • IPMI (ILO, DRAC, etc)
  • Appliances management interfaces
  • Management interfaces of servers

They also carry sensitive protocols like SNMP, backup traffic to not interfere with the "production" traffic. OoB networks are, based on their criticality, pretty well hardened with very limited access through bastion hosts. Sometimes, they are so well protected that remote access is not allowed and could lead to critical situations like the recent Facebook downtime due to a BGP issue[1].

But OoB networks can also be used for other purposes: during a security incident. It's recommended to not allow Incident Handlers to use the corporate network to exchange information.

A few days ago, an interesting tweet has been posted by @vxunderground[2]. Apparently, the Ragnar Locker ransomware group was able to access a Slack channel used by the organization in charge of the investigations. 

(Image source: vxunderground's Twitter account)

As you can see on top of the screenshot, there is the classic Remote Desktop Client banner. Probably, an Incident Handler was connected to the Teams channel from a workstation on the compromised network and the attacker was still present... Teams is an "external service" and traffic to Teams is encrypted but if the client or the browser can be accessed, it's too late!


Xavier Mertens (@xme)
Senior ISC Handler - Freelance Cyber Security Consultant

0 comment(s)

If you have more information or corrections regarding our diary, please share.

Recent Diaries

A Review of Year 2021
Dec 4th 2021
1 day ago by Guy (0 comments)

The UPX Packer Will Never Die!
Dec 3rd 2021
3 days ago by Xme (0 comments)

TA551 (Shathak) pushes IcedID (Bokbot)
Dec 3rd 2021
3 days ago by Brad (0 comments)

Info-Stealer Using to Exfiltrate Data
Dec 1st 2021
5 days ago by Xme (0 comments)

Hunting for PHPUnit Installed via Composer
Nov 30th 2021
6 days ago by Johannes (0 comments)

Wireshark 3.6.0 Released
Nov 29th 2021
1 week ago by DidierStevens (0 comments)

View All Diaries →

Latest Discussions

Dshield Sensor
created Jun 8th 2021
5 months ago by Rick (0 replies)

API port data
created Apr 25th 2021
7 months ago by JJ (1 reply)

RSS feed containing non-XML compatible characters
created Apr 14th 2021
7 months ago by Anonymous (1 reply)

Handler's Diary (Full text) RSS Feeds stopt working due to a typo
created Mar 5th 2021
9 months ago by (0 replies)

port_scan issue in Snort3
created Feb 23rd 2021
9 months ago by astraea (0 replies)

View All Forums →

Latest News

Top Diaries

Shadow IT Makes People More Vulnerable to Phishing
Nov 10th 2021
3 weeks ago by Xme (0 comments)

"Summer of SAM": Microsoft Releases Guidance for CVE-2021-36934
Jul 22nd 2021
4 months ago by Johannes (0 comments)

Securing and Optimizing Networks: Using pfSense Traffic Shaper Limiters to Combat Bufferbloat
Jul 12th 2021
4 months ago by Johannes (0 comments)

DIY CD/DVD Destruction - Follow Up
Jul 4th 2021
5 months ago by DidierStevens (0 comments)

The Importance of Out-of-Band Networks
Dec 6th 2021
7 hours ago by Xme (0 comments)