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The critical role played by email has led to a range of extension protocols (e.g., SPF, DKIM, DMARC) designed to protect against the spoofing of email sender domains. These protocols are complex as is, but are further complicated by automated email forwarding — used by individual users to manage multiple accounts and by mailing lists to redistribute messages. In this paper, we explore how such email forwarding and its implementations can break the implicit assumptions in widely deployed anti-spoofing protocols. Using large-scale empirical measurements of 20 email forwarding services (16 leading email providers and four popular mailing list services), we identify a range of security issues rooted in forwarding behavior and show how they can be combined to reliably evade existing anti-spoofing controls. We further show how these issues allow attackers to not only deliver spoofed email messages to prominent email providers (e.g., Gmail, Microsoft Outlook, and Zoho), but also reliably spoof email on behalf of tens of thousands of popular domains including sensitive domains used by organizations in government (e.g., state.gov), finance (e.g., transunion.com), law (e.g., perkinscoie.com) and news (e.g., washingtonpost.com) among others. 

Cybersecurity companies routinely rely on telemetry from inside customer networks to collect intelligence about new online threats. However, the mechanism by which such intelligence is gathered can itself create new security risks. In this paper, we explore one such subtle situation that arises from an intelligence gathering feature present in FireEye's widely-deployed passive deep-packet inspection appliances. In particular, FireEye's systems will report back to the company Web requests containing particular content strings of interest. Based on these reports, the company then schedules independent requests for the same content using distributed Internet proxies. By broadly scanning the Internet using a known trigger string we are able to reverse engineer how these measurements work. We show that these side-effects provide a means to empirically establish which networks and network links are protected by such appliances. Further, we also show how to influence the associated proxies to issue requests to any URL. 

Mutually Agreed Norms on Routing Security (MANRS) is an industry-led initiative to improve Internet routing security by encouraging participating networks to implement a series of mandatory or recommended actions. MANRS members must register their IP prefixes in a trusted routing database and use such information to prevent propagation of invalid routing information. MANRS membership has increased significantly in recent years, but the impact of the MANRS initiative on the overall Internet routing security remains unclear. In this paper, we provide the first independent look into the MANRS ecosystem by using publicly available data to analyze the routing behavior of participant networks. We quantify MANRS participants' level of conformance with the stated requirements, and compare the behavior of MANRS and non-MANRS networks. While not all MANRS members fully comply with all required actions, we find that they are more likely to implement routing security practices described in MANRS actions. We assess the relevance of the MANRS effort in securing the overall routing ecosystem. We found that as of May 2022, over 83% of MANRS networks were conformant to the route filtering requirement by dropping BGP messages with invalid information according to authoritative records, and over 95% were conformant to the routing information facilitation requirement, registering their resources in authoritative databases. 

In 2019, the US Department of Homeland Security issued an emergency warning about DNS infrastructure tampering. This alert, in response to a series of attacks against foreign government websites, highlighted how a sophisticated attacker could leverage access to key DNS infrastructure to then hijack traffic and harvest valid login credentials for target organizations. However, even armed with this knowledge, identifying the existence of such incidents has been almost entirely via post hoc forensic reports (i.e., after a breach was found via some other method). Indeed, such attacks are particularly challenging to detect because they can be very short lived, bypass the protections of TLS and DNSSEC, and are imperceptible to users. Identifying them retroactively is even more complicated by the lack of fine-grained Internet-scale forensic data. This paper is a first attempt to make progress at this latter goal. Combining a range of longitudinal data from Internet-wide scans, passive DNS records, and Certificate Transparency logs, we have constructed a methodology for identifying potential victims of sophisticated DNS infrastructure hijacking and have used it to identify a range of victims (primarily government agencies), both those named in prior reporting, and others previously unknown. 

In this paper, we explore a domain hijacking vulnerability that is an accidental byproduct of undocumented operational practices between domain registrars and registries. We show how over the last nine years over 512K domains have been implicitly exposed to the risk of hijacking, affecting names in most popular TLDs (including .com and .net) as well as legacy TLDs with tight registration control (such as .edu and .gov). Moreover, we show that this weakness has been actively exploited by multiple parties who, over the years, have assumed control over 163K domains without having any ownership interest in those names. In addition to characterizing the nature and size of this problem, we also report on the efficacy of the remediation in response to our outreach with registrars.