Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Perimeter

9/1/2010
08:30 AM
John H. Sawyer
John H. Sawyer
Commentary
50%
50%

Finding Exposed Devices On Your Network

When browsing through SHODAN, it never ceases to amaze me what I can find. How is it that people think it's okay to leave their printers, routers, fiber channel switches, and industrial control systems completely open to the Internet?

When browsing through SHODAN, it never ceases to amaze me what I can find. How is it that people think it's okay to leave their printers, routers, fiber channel switches, and industrial control systems completely open to the Internet?In case you're not sure what SHODAN is, I've mentioned SHODAN a few times in previous articles and blogs like "Gaining A Foothold By Exploiting VxWorks Vulns." It's been referred to as a rainbow table for Internet-accessible computers because it provides a searchable index of service banners retrieved from HTTP, HTTPS, FTP, SSH, and telnet services on the Internet without the need to do any of your own scanning.

When I was looking at the VxWorks vulnerability, I found vulnerable printers, network switches, fiber channel switches, and industrial control systems (or SCADA) equipment through some simple searches that are mentioned in this blog.

So I'm left wondering who thought it was a good idea to put these devices on the Internet without some sort of protection in place. Is there no change management procedures at these organizations where someone should be monitoring what's taking place on the network? Surely someone has to provision the public IP for use for the devices. Why aren't they asking what the IP will be used for and if the device is being locked down?

Sure, you can use SHODAN to check your netblocks for exposed devices that you might not be aware of, but why not be a little more proactive? Isn't proactive security better than reactive security? Or more to the point, wouldn't you rather find out about a new exposed device on you network before an attacker does?

There are a couple ways to go about this. The first is setting up some simple network scans using Nmap. It could be done daily or weekly, but I wouldn't recommend going as long as a month in between scans. Be sure to set up the scans to save the output to the Nmap XML format. Once you have more than one scan, you can use the Ndiff utility to compare the two scans and determine if there are any state changes for hosts, ports, service versions, operating systems, and the output of scripts.

The Nmap route is cheap and easy to implement, but if you have a nice netflow analysis solution like Lancope's StealthWatch, it can be done even easier. All of the netflow monitoring tools I've seen have an alert option that will notify admins when a new host is seen communicating on the network. I've also seen alerts for when a host begins acting as a server for the first time. For example, if a host is on the network and begins accepting and responding to requests on TCP port 443 for the first time, admins will receive an alert.

Security teams are often the last ones to know when new systems are brought online, but they don't have to be. Using the tools above, security can know when new systems show up on the network and take appropriate actions such as a vulnerability scan, and confirm that the device is authorized and not some rogue wireless router an employee decided to plug in so they could use their new iPad.

John H. Sawyer is a senior security engineer on the IT Security Team at the University of Florida. The views and opinions expressed in this blog are his own and do not represent the views and opinions of the UF IT Security Team or the University of Florida. When John's not fighting flaming, malware-infested machines or performing autopsies on blitzed boxes, he can usually be found hanging with his family, bouncing a baby on one knee and balancing a laptop on the other. Special to Dark Reading.

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
For Cybersecurity to Be Proactive, Terrains Must Be Mapped
Craig Harber, Chief Technology Officer at Fidelis Cybersecurity,  10/8/2019
A Realistic Threat Model for the Masses
Lysa Myers, Security Researcher, ESET,  10/9/2019
USB Drive Security Still Lags
Dark Reading Staff 10/9/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Current Issue
7 Threats & Disruptive Forces Changing the Face of Cybersecurity
This Dark Reading Tech Digest gives an in-depth look at the biggest emerging threats and disruptive forces that are changing the face of cybersecurity today.
Flash Poll
2019 Online Malware and Threats
2019 Online Malware and Threats
As cyberattacks become more frequent and more sophisticated, enterprise security teams are under unprecedented pressure to respond. Is your organization ready?
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-17545
PUBLISHED: 2019-10-14
GDAL through 3.0.1 has a poolDestroy double free in OGRExpatRealloc in ogr/ogr_expat.cpp when the 10MB threshold is exceeded.
CVE-2019-17546
PUBLISHED: 2019-10-14
tif_getimage.c in LibTIFF through 4.0.10, as used in GDAL through 3.0.1 and other products, has an integer overflow that potentially causes a heap-based buffer overflow via a crafted RGBA image, related to a "Negative-size-param" condition.
CVE-2019-17547
PUBLISHED: 2019-10-14
In ImageMagick before 7.0.8-62, TraceBezier in MagickCore/draw.c has a use-after-free.
CVE-2019-17501
PUBLISHED: 2019-10-14
Centreon 19.04 allows attackers to execute arbitrary OS commands via the Command Line field of main.php?p=60807&type=4 (aka the Configuration > Commands > Discovery screen).
CVE-2019-17539
PUBLISHED: 2019-10-14
In FFmpeg before 4.2, avcodec_open2 in libavcodec/utils.c allows a NULL pointer dereference and possibly unspecified other impact when there is no valid close function pointer.