February 8, 2020

As an early domain name investor, Mike O’Connor had by 1994 snatched up several choice online destinations, including bar.com, cafes.com, grill.com, place.com, pub.com and television.com. Some he sold over the years, but for the past 26 years O’Connor refused to auction perhaps the most sensitive domain in his stable — corp.com. It is sensitive because years of testing shows whoever wields it would have access to an unending stream of passwords, email and other proprietary data belonging to hundreds of thousands of systems at major companies around the globe.

Now, facing 70 and seeking to simplify his estate, O’Connor is finally selling corp.com. The asking price — $1.7 million — is hardly outlandish for a 4-letter domain with such strong commercial appeal. O’Connor said he hopes Microsoft Corp. will buy it, but fears they won’t and instead it will get snatched up by someone working with organized cybercriminals or state-funded hacking groups bent on undermining the interests of Western corporations.

One reason O’Connor hopes Microsoft will buy it is that by virtue of the unique way Windows handles resolving domain names on a local network, virtually all of the computers trying to share sensitive data with corp.com are somewhat confused Windows PCs. More importantly, early versions of Windows actually encouraged the adoption of insecure settings that made it more likely Windows computers might try to share sensitive data with corp.com.

At issue is a problem known as “namespace collision,” a situation where domain names intended to be used exclusively on an internal company network end up overlapping with domains that can resolve normally on the open Internet.

Windows computers on an internal corporate network validate other things on that network using a Microsoft innovation called Active Directory, which is the umbrella term for a broad range of identity-related services in Windows environments. A core part of the way these things find each other involves a Windows feature called “DNS name devolution,” which is a kind of network shorthand that makes it easier to find other computers or servers without having to specify a full, legitimate domain name for those resources.

For instance, if a company runs an internal network with the name internalnetwork.example.com, and an employee on that network wishes to access a shared drive called “drive1,” there’s no need to type “drive1.internalnetwork.example.com” into Windows Explorer; typing “\\drive1\” alone will suffice, and Windows takes care of the rest.

But things can get far trickier with an internal Windows domain that does not map back to a second-level domain the organization actually owns and controls. And unfortunately, in early versions of Windows that supported Active Directory — Windows 2000 Server, for example — the default or example Active Directory path was given as “corp,” and many companies apparently adopted this setting without modifying it to include a domain they controlled.

Compounding things further, some companies then went on to build (and/or assimilate) vast networks of networks on top of this erroneous setting.

Now, none of this was much of a security concern back in the day when it was impractical for employees to lug their bulky desktop computers and monitors outside of the corporate network. But what happens when an employee working at a company with an Active Directory network path called “corp” takes a company laptop to the local Starbucks?

Chances are good that at least some resources on the employee’s laptop will still try to access that internal “corp” domain. And because of the way DNS name devolution works on Windows, that company laptop online via the Starbucks wireless connection is likely to then seek those same resources at “corp.com.”

In practical terms, this means that whoever controls corp.com can passively intercept private communications from hundreds of thousands of computers that end up being taken outside of a corporate environment which uses this “corp” designation for its Active Directory domain.


That’s according to Jeff Schmidt, a security expert who conducted a lengthy study on DNS namespace collisions funded in part by grants from the U.S. Department of Homeland Security. As part of that analysis, Schmidt convinced O’Connor to hold off selling corp.com so he and others could better understand and document the volume and types of traffic flowing to it each day.

During an eight month analysis of wayward internal corporate traffic destined for corp.com in 2019, Schmidt found more than 375,000 Windows PCs were trying to send this domain information it had no business receiving — including attempts to log in to internal corporate networks and access specific file shares on those networks.

For a brief period during that testing, Schmidt’s company JAS Global Advisors accepted connections at corp.com that mimicked the way local Windows networks handle logins and file-sharing attempts.

“It was terrifying,” Schmidt said. “We discontinued the experiment after 15 minutes and destroyed the data. A well-known offensive tester that consulted with JAS on this remarked that during the experiment it was ‘raining credentials’ and that he’d never seen anything like it.”

Likewise, JAS temporarily configured corp.com to accept incoming email.

“After about an hour we received in excess of 12 million emails and discontinued the experiment,” Schmidt said. “While the vast majority of the emails were of an automated nature, we found some of the emails to be sensitive and thus destroyed the entire corpus without further analysis.”

Schmidt said he and others concluded that whoever ends up controlling corp.com could have an instant botnet of well-connected enterprise machines.

“Hundreds of thousands of machines directly exploitable and countless more exploitable via lateral movement once in the enterprise,” he said. “Want an instant foothold into about 30 of the world’s largest companies according to the Forbes Global 2000? Control corp.com.”


Schmidt’s findings closely mirror what O’Connor discovered in the few years corp.com was live on the Internet after he initially registered it back in 1994. O’Connor said early versions of a now-defunct Web site building tool called Microsoft FrontPage suggested corporation.com (another domain registered early on by O’Connor) as an example domain in its setup wizard.

That experience, portions of which are still indexed by the indispensable Internet Archive, saw O’Connor briefly redirecting queries for the domain to the Web site of a local adult sex toy shop as a joke. He soon got angry emails from confused people who’d also CC’d Microsoft co-founder Bill Gates.

Archive.org’s index of corp.com from 1997, when its owner Mike O’Connor briefly enabled a Web site mainly to shame Microsoft for the default settings of its software.

O’Connor said he also briefly enabled an email server on corp.com, mainly out of morbid curiosity to see what would happen next.

“Right away I started getting sensitive emails, including pre-releases of corporate financial filings with The U.S. Securities and Exchange Commission, human resources reports and all kinds of scary things,” O’Connor recalled in an interview with KrebsOnSecurity. “For a while, I would try to correspond back to corporations that were making these mistakes, but most of them didn’t know what to do with that. So I finally just turned it off.”


Microsoft declined to answer specific questions in response to Schmidt’s findings on the wayward corp.com traffic. But a spokesperson for the company shared a written statement acknowledging that “we sometimes reference ‘corp’ as a label in our naming documentation.”

“We recommend customers own second level domains to prevent being routed to the internet,” the statement reads, linking to this Microsoft Technet article on best practices for setting up domains in Active Directory.

Over the years, Microsoft has shipped several software updates to help decrease the likelihood of namespace collisions that could create a security problem for companies that still rely on Active Directory domains that do not map to a domain they control.

But both O’Connor and Schmidt say hardly any vulnerable organizations have deployed these fixes for two reasons. First, doing so requires the organization to take down its entire Active Directory network simultaneously for some period of time. Second, according to Microsoft applying the patch(es) will likely break or at least slow down a number of applications that the affected organization relies upon for day-to-day operations.

Faced with either or both of these scenarios, most affected companies probably decided the actual risk of not applying these updates was comparatively low, O’Connor said.

“The problem is that when you read the instructions for doing the repair, you realize that what they’re saying is, ‘Okay Megacorp, in order to apply this patch and for everything to work right, you have to take down all of your Active Directory services network-wide, and when you bring them back up after you applied the patch, a lot of your servers may not work properly’,” O’Connor said.

Curiously, Schmidt shared slides from a report submitted to a working group on namespace collisions suggesting that at least some of the queries corp.com received while he was monitoring it may have come from Microsoft’s own internal networks.

Image: JAS Global Advisors

“The reason I believe this is Microsoft’s issue to solve is that someone that followed Microsoft’s recommendations when establishing an active directory several years back now has a problem,” Schmidt said.

“Even if all patches are applied and updated to Windows 10,” he continued. “And the problem will persist while there are active directories named ‘corp’ – which is forever. More practically, if corp.com falls into bad hands, the impact will be on Microsoft enterprise clients – and at large scale – paying, Microsoft clients they should protect.”

O’Connor said Microsoft actually offered to buy the domain several years back for $20,000. He turned them down, saying that at the time he thought it was too low and didn’t reflect the market value of the domain.

Asked why he didn’t just give corp.com to Microsoft as an altruistic gesture, O’Connor said he believes the software giant ought to be accountable for its products and mistakes.

“It seems to me that Microsoft should stand up and shoulder the burden of the mistake they made,” he said. “But they’ve shown no real interest in doing that, and so I’ve shown no interest in giving it to them. I don’t really need the money. I’m basically auctioning off a chemical waste dump because I don’t want to pass it on to my kids and burden them with it. My frustration here is the good guys don’t care and the bad guys probably don’t know about it. But I expect the bad guys would like it.”

Further reading:

Mitigating the Risk of DNS Namespace Collisions (PDF)

DEFCON 21 – DNS May Be Hazardous to your Health (Robert Stucke)

Mitigating the Risk of Name Collision-Based Man-in-the-Middle Attacks (PDF)

Update, 6:22 p.m. ET: Added the bit at the end about the $20,000 offer a few years back from Microsoft, a detail that I somehow omitted from the original story.

78 thoughts on “Dangerous Domain Corp.com Goes Up for Sale

  1. DH

    If you don’t use the FQDN , there is a config file where it will define domains to append to your query. You can change all of that.

    Each corporation should have properly set up their AD to append their company domain and not a default example that was provided. They had a very, very long time to correct their AD structure to properly address this issue (when they connected their internal company to the internet). Besides the recommendation to never use the AD domain name to match DNS zone (can really screw with the web services with the split-horizon), PTR records and lmhosts / hosts changes on the laptops should be able to override this issue.

    In defense of MS, do we only punish the company for people who use default passwords? Yes, it is a bad practice, but I think the guy should have taken the $20K and not be subject to the cyber equivalent of “Eminent domain”.

    1. Anon404

      I think thats nonsense. MS, as they frequently have, made a VERY bad decision when building Windows, one that leaves many of their customers vulnerable, including themselves. THEY, should have properly fixed the issue a long time ago rather than placing all the blame on their customers. It was MS who screwed up in the first place. Why should small companies risk their business when MS is a multibillion dollar company who could easily shoulder the cost? Its just as silly as blaming individuals for all the pollution and global warming when in reality, the vast majority of all harmful pollution comes from a handful of large corporations.

  2. Target Audience

    My bet is on NSA getting Microsoft to buy it, so they have access without obvious exposure. I mean you gotta get some perks from a $10B government Azure contract.

  3. bobcov

    I hope the guy gets several million for his property. I see nothing wrong with him getting a payday. Nothing at all amiss ethically. However, are there any lawyers here who could answer if Microsoft sold a defective product? Seems to me they are legally on the hook for the problem they caused. Maybe not 100%, but seeing as they don’t seem to be doing much of anything to mitigate the problem (such as snap up this domain), their percentage of fault could be north of 50. They as much admitted to a problem by making an offer in the first place.

    1. Jim B

      Nobody can sue Microsoft; they have agents that refuse to accept service of process, and if you hire a process server to ambush them coming home at night then their lawyers smother you with countersuits and discovery demands that run you broke before you get to trial. Class action would be the only strategy, but assembling a class of Megacorp victims would be near impossible because they each have an army of risk averse lawyers that can read the indemnification clauses in Microsoft’s software EULAs. Game over.

  4. John S

    If he truly believes that organized crime will buy the domain and use it for a botnet or to defraud someone, then he is morally copable if he just sells it to the highest bidder. If he really thinks that corp.com is too powerful a domain name to fall into the wrong hands, then he should take steps to ensure that doesn’t happen. Money is not king. You can’t sell guns to a mob boss and then try to wash your hands of moral copability.

  5. Ted Roche

    Amazingly, DangerousDomainCorp.com is available for registration. How has an evil supervillian not snatched that up?

  6. Catwhisperer

    Excellent and eye opening report, Brian. And nobody knew, even people with years of experience. Something old and insidious to worry about, but new to many eyes…

  7. __sky.captain__

    Microsoft has addressed this on its newer platforms. The capability Windows has to let you connect to a server by using the name MYSERVER instead of MYSERVER.mycorp.com is called DNS devolution, and Mr. Krebs linked to a good article about it. That same article contains this:

    “The (Windows) DNS devolution logic has changed as follows:

    “If the number of labels in the AD forest root domain’s DNS name is one or a machine’s primary DNS suffix doesn’t end with the forest root domain’s DNS name, DNS devolution is automatically disabled. For example, if a computer is a member of the mycompany.com domain and the forest root domain name is mycompany.fl.us, devolution is disabled (mycompany.com does not end with mycompany.fl.us).

    “If a machine’s primary DNS suffix ends with the forest root domain’s DNS name, the devolution level is automatically set to the number of labels in the forest root domain. For example, if the computer is a member of the research.mycompany.fl.us domain and the forest root domain name is mycompany.fl.us, the devolution level is set to three (which matches the number of labels in mycompany.fl.us).”

    These adjustments put modern Windows platforms in a correct posture regarding DNS devolution.

  8. Doug In Milwaukee

    Corp.Com { .net .org } is but one example of At-Risk domains. Local.Com, LAN.Com, and any other “made up” NetBIOS single-label Top Level domain (subject to auto-appending .com etc) are all similarly exposed.

    IMO Microsoft made three egregious errors regarding IP DNS in the early 1990’s. First was the decision to make Windows auto-append common Top Level Domain names (TLD) to single-label queries. Second was their automatic, embedded use of unregistered TLDs (e.g. .Local) in products such as Small Business Server. And, most importantly, third was their cavalier disregard for proper usage of Internet Engineering Task Force (IETF)-promulgated standards in writing their documentation.

    Specifically, they consistently failed to follow RFC2606 Reserved Names For Documentation such as “Example.Com” or RFC5737 (with roots back thirty years to RFC1166 et al) IP Addresses Reserved For Documentation such as 192 0.2.0/24.

    Just this morning I’d been reading a current Windows version document from Microsoft which used a 172.51.x.x address as example. By context, I could tell the inexperienced Microsoft writer probably intended to use an RFC1918 (i.e Private/internal) Class B address ( through However, instead they’ve published a public address actually assigned to T-Mobile, whose network will be similarly hosed due to Microsoft Mistakes. I have read, and negatively fed back in-line comments, Microsoft documentation time and again for over a quarter century which regularly contained such errors.

    The problems of Root Servers being deluged by unanswerable queries, and of answerable but unregistered queries, are
    well documented as hugely detrimental to the security and stability of the Internet. Attempts such as RFC7534’s AS112 address space interception, and RFC8375′ sacrificial Home.ARPA domain are mere fingers in the dike. To solve, the deluge must be addressed by often ersatz Administrators (of which nearly every home user is) properly configuring their equipment. Vendors and documentors must set Best Current Practice examples in their products in order to teach and in order to be compliant Out Of The Box.

    Microsoft, having failed miserably in being a good Network Citizen in fostering the problem, should indeed purchase and capture the Corp.Com domain, and others, and then donate the names to the IANA for inclusion in the Special Use reservations.


    1. DG

      What Doug said! ^^^^^^

      Developers at Microsoft have _always_ seemed to have this attitude of “We’ll write whatever we want and you’ll do things our way because ‘We RULE!'”

      Even during the days of DOS 2.0, MS completely ignored prior usage of 3 letter file extension naming conventions for mature competitor released products. All without including any kind of ‘file magic’ to differentiate their files from competitors files such as used in ‘nix at the time.

      The response I always got when I noted these issues to MS was basically either complete silence or the equivalent of “Sucks to be you!” Of course, I wasn’t a large corporation or governmental body.

      Naming collisions? MS has fostered naming collisions, silent partial expansions, silent (usually undocumented) attempts to compensate for user errors and other problem inducing methodology since _forever_. They didn’t care then. They didn’t care during my whole career (I’m retired now) and as far as I can tell, they still don’t care.

      Compilers should never try to guess and fix programmer errors. Reporting errors help programmers get things right.

      Applications should _never_ silently try to fix user errors.

      Applications should _never_ silently ignore application errors.

      Application documentation should always have clear examples which cannot be cut and pasted and which clearly indicate they are only ‘examples’.

      MS has often sold management on the concept that ‘anyone’ can install their products. That ‘anyone’ can be a professional publisher, accountant, web site builder, server administrator. That concept just doesn’t fly. It doesn’t surprise me at all at the number of major installations out there that have slavishly followed MS’s documentation and gotten it wrong.

      MS take responsibility by doing something like buying corp[.]com and other domains with like collision issues? HAH!

  9. Microsoft monthly payments

    Reading this reminds me why I despise Microsoft. Yes–I’m projecting. I hate renting bloated software. If Microsoft imploded today; would the world be better off? Throw Apple, and Adobe on the implode list too.

Comments are closed.