Abandoned subdomains pose security risk for businesses

Attackers could hijack subdomains pointed by companies at external services they no longer use, researchers say

Many companies set up subdomains for use with external services, but then forget to disable them when they stop using those services, creating a loophole for attackers to exploit.

Because many service providers don't properly validate the ownership of subdomains pointed at their servers, attackers can set up new accounts and abuse subdomains forgotten by companies by claiming them as their own.

Removing or updating DNS entries for subdomains that are no longer actively used sounds like something that should be common procedure, but according to researchers from Detectify, a Stockholm-based provider of website security scanning services, this type of oversight is actually quite widespread among companies.

"We've identified at least 17 Service Providers which do not handle the subdomain ownership verification properly -- allowing this vulnerability to be exploited, Heroku, Github, Bitbucket, Squarespace, Shopify, Desk, Teamwork, Unbounce, Helpjuice, HelpScout, Pingdom, Tictail, Campaign Monitor, CargoCollective, StatusPage.io and Tumblr," the Detectify researchers said in a blog post earlier this week.

"We've also identified at least 200 organizations which are currently affected," the researchers said. "In many cases, we are talking NASDAQ-listed, top 100 Alexa rank domains that basically allowed us to set up a Hello World on their domains."

The risk to website owners depends on what can be done on a third-party service once a domain is pointed to it. If the service allows users to set up Web pages or Web redirects, attackers could exploit the situation to launch credible phishing attacks by creating rogue copies of the main website.

In an attack scenario described by Detectify, a company might set up a subdomain for use with an external support ticketing service, but later close its account and forget to delete the subdomain. Attackers could then create a new account with the same service and claim the company's subdomain, which already has the needed DNS settings, as their own, allowing them to set up a fake website on it.

Some of the subdomains exposed to this form of hijacking that were found by Detectify belonged to various types of organizations including government agencies, health services providers, insurance companies and banks.

The security firm created an online tool that can help organizations check if they have subdomains vulnerable to this attack. The tool requires users to first prove they have control over the domains they intend to scan by using several methods.

Some service providers use similar checks. For example, to use Google Apps with a custom domain name the domain administrator needs to upload a specific HTML file to the Web server hosting the domain, to add a TXT or CNAME record in their domain's DNS settings or to add a specific meta tag to their website's home page. All these methods are forms of domain ownership verification.

Join the CSO newsletter!

Error: Please check your email address.

Tags GitHubonline safetysecurityAccess control and authenticationherokuExploits / vulnerabilitiesDetectify

More about GoogleNASDAQ

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Lucian Constantin

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts