The attack hinges on a common mistake made by large organizations…

An article review.

When evaluating a suspicious link, you probably scrutinize the URL to make sure it’s the site you intended to go to—not one that is slightly misspelled or has a zero in place of an O, for example—but what if the bad guys have access to a URL on a valid, working domain? A new attack can give hackers exactly that, and it all depends on domain owners making a minor, common mistake.

The attack, announced in June by two Israeli security firms, focuses on temporary subdomains created by a company for promotions or other special events. After the end of the promotion, the company spins down its cloud hosting for the promotional site—but forgets to remove the DNS records for that subdomain. At this point, a hacker with an account at that same cloud hosting provider can potentially create their own host, request the name used by the company’s legitimate cloud instance, and assume control of the subdomain.

With control of a valid subdomain, hackers can then set and access cookies and authentication tokens for that domain and could even appear to have a valid security certificate, making it nearly impossible for the user to know they are on a malicious site.

The good news is this attack, while potentially very damaging, requires a specific set of circumstances to be achieved. The bad news is, according to the researchers, large corporations make this kind of mistake often due to poor communications between the teams responsible for DNS records, and the teams responsible for promotional events.

Since this attack can result in a site that holds up to reasonable scrutiny, there are not many things an end user can do to avoid it–other than check to see if the promotion or event the URL was created for has ended. The impetus is on corporate network operations teams to stay on top of their DNS records, protecting both their users and their reputation.

Original article by Jim Salter writing for Ars Technica.