Email Typosquatting
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Email Typosquatting Janos Szurdi Nicolas Christin Carnegie Mellon University Carnegie Mellon University [email protected] [email protected] ABSTRACT 1 INTRODUCTION While website domain typosquatting is highly annoying for le- Domain typosquatting is the act of registering a domain name very gitimate domain operators, research has found that it relatively similar to an existing, legitimate, domain, in an effort to capture rarely presents a great risk to individual users. However, any appli- some of the traffic destined for the original domain. Domain ty- cation (e.g., email, ftp,...) relying on the domain name system for posquatting exploits the propensity of users to make typographical name resolution is equally vulnerable to domain typosquatting, and errors when typing domain names—as opposed to clicking on links— consequences may be more dire than with website typosquatting. and is frequently used for financial profit. For instance, somebody This paper presents the first in-depth measurement study of registering googe.com would immediately receive large amounts email typosquatting. Working in concert with our IRB, we regis- of traffic meant for google.com. That traffic could then in turn tered 76 typosquatting domain names to study a wide variety of user be monetized, by showing ads or setting up drive-by-downloads. mistakes, while minimizing the amount of personal information ex- Domain typosquatting has been shown to be profitable [18, 24], posed to us. In the span of over seven months, we received millions while requiring no technical skill. of emails at our registered domains. While most of these emails In some jurisdictions, domain typosquatting is considered illegal, are spam, we infer, from our measurements, that every year, three and may trigger trademark infringement cases.1 In 1999, ICANN, of our domains should receive approximately 3,585 “legitimate” the authority which regulates domain names on the Internet, cre- emails meant for somebody else. Worse, we find, by examining a ated the Uniform Domain Name Dispute Resolution Policy (UDRP) small sample of all emails, that these emails may contain sensitive as a solution for trademark owners to claim cybersquatting or ty- information (e.g., visa documents or medical records). posquatting domain names [21]. We then project from our measurements that 1,211 typosquatting Thus far, most of the studies in the related literature have solely domains registered by unknown entities receive in the vicinity focused on web typosquatting, that is, domain typosquatting used of 800,000 emails a year. Furthermore, we find that millions of to illicitly acquire “page views.” However, domain typosquatting registered typosquatting domains have MX records pointing to only can be equally used with other target applications—ssh, ftp, email, a handful of mail servers. However, a second experiment in which and so forth. we send “honey emails” to typosquatting domains only shows very This paper is the first in-depth study to focus on email typosquat- limited evidence of attempts at credential theft (despite some emails ting, in which miscreants could register domain names mimicking being read), meaning that the threat, for now, appears to remain those of large email providers to capture emails. Even though typing theoretical. mistakes may be fairly rare, typosquatting a large email provider (e.g., gmail.com) could remain a profitable endeavor by virtue of CCS CONCEPTS the number of emails passing through the service. Indeed, while • Security and privacy → Human and societal aspects of se- most emails illicitly received would be of limited use to the attacker, curity and privacy; Network security; • Networks → Network some could contain sensitive information that could yield large measurement; payoffs for the attacker, and cause considerable losses to the victim. We put this hypothesis to the test in this paper. Specifically, we KEYWORDS register 76 email typosquatting domains, collect data from these domains for more than seven months (June 4, 2016–January 15, Domain name, Typosquatting, Abuse, Measurement, Ethics 2017), and—working in concert with our Internal Review Board (IRB)—design a protocol to process the emails we receive to deter- ACM Reference Format: Janos Szurdi and Nicolas Christin. 2017. Email Typosquatting. In Proceedings mine the potential harm email domain typosquatting might inflict of IMC ’17: Internet Measurement Conference . ACM, New York, NY, USA, on users, as well as its potential benefits to attackers (Section 4). 13 pages. https://doi.org/10.1145/3131365.3131399 We discover that a number of actors already have the infrastruc- ture necessary for bulk email domain typosquatting (Section 5). Extrapolating from our observations through regression analysis Permission to make digital or hard copies of all or part of this work for personal or (Section 6), we find that setting up the necessary infrastructure classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation costs attackers only in the order of a couple of cents per email, and on the first page. Copyrights for components of this work owned by others than ACM that they can expect to receive hundreds of thousands of emails must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a over a few months. However, by actively sending “honey emails” fee. Request permissions from [email protected]. containing credentials, we discover, that even though a lot of these IMC ’17: Internet Measurement Conference , November 1–3, 2017, London, United Kingdom © 2017 Association for Computing Machinery. ACM ISBN 978-1-4503-5118-8/17/11...$15.00 1See, e.g., in the U.S., the Federal Trademark Dilution Act, or FTDA, and the Anti- https://doi.org/10.1145/3131365.3131399 cybersquatting Consumer Protection Act, ACPA. IMC ’17: Internet Measurement Conference , November 1–3, 2017, London, United Kingdom J. Szurdi and N. Christin emails are accepted, they are not actually read (Section 7), meaning Distance metrics. We use two metrics to characterize the distance that email typosquatting does not appear, for now, to be monetized. between various domain names. The Damerau-Levenshtein distance [16] is the minimum number of operations (deletion, addition, sub- stitution, or transposition of two neighboring characters). Papers 2 RELATED WORK on typosquatting often rely on Damerau-Levenshtein distance of Our work broadly inscribes itself in the general line of research one (“DL-1”) to detect typosquatting domains. Moore and Edelman in online crime measurements, which has been an extremely ac- define the fat-finger distance as “the minimum number of insertions, tive area of research over the past fifteen years or so. Rather than deletions, substitutions or transpositions using letters adjacent on providing a comprehensive overview of the entire area, we refer a QWERTY keyboard to transform one string into another.” [24] the reader to recent survey papers in the field [12, 28]. Here, we A fat-finger distance of one (FF-1) implies a DL-1 distance. The focus instead on the narrower body of work that has attempted visual distance measures how different the mistyped character looks to characterize the prevalence of domain typosquatting, and its compared to the original character. We use a set of heuristic rules economic effects, and outline how our work builds on more than to compute the visual distance, which incorporate how confusing fourteen years of research in the community. alphabet letters with numbers (e.g., “o” and “O,” “1” and “l”) is more Most typosquatting papers have focused on web typosquatting, likely to happen than confusing two (different) letters or numbers. which targets users who make a mistake while typing an URL in Typosquatting domains. The target domain name refers to any their browser. In 2003, Edelman undertook the first case study of one domain name targeted by typosquatters. Previous work on web typosquatter who registered, at the time, thousands of domains [17]. typosquatting usually relies on Alexa rankings [1] to identify target Subsequently, a number of efforts [13–15, 31] proposed methods to domains. detect typosquatting domains targeting popular websites, as ranked We adopt Szurdi et al.’s taxonomy [27] to clearly differentiate by the Alexa service [1], and to differentiate legitimate domains lexically close domains from true typosquatting domain names. from typosquatting domains [27]. Some of these studies suggest Generated typo domains (“gtypos”) are “domain names which are that monetization is achieved through domain parking – the act of lexically similar (e.g. at DL-1) to some set of target domains.” Candi- monetizing otherwise empty web pages with advertisements. date typo domains (“ctypos”) are “the subset of registered domains Moore and Edelman [24] discussed monetization of typosquat- within the gtypo set which have been registered.” Finally, typosquat- ting, and showed that miscreants might be relying on Google Ad- ting domains are candidate typo domains that “(i) [were] registered Words to select which typosquatting domains to register. Along to benefit from traffic intended for a target domain,” and “(ii) that the same lines, Agten et al. [11] provided a longitudinal study of [are] the property of a different entity.” monetization strategies of typosquatting