An official website of the United States government
Security research has made extensive use of exhaustive Internet-wide scans over the recent years, as they can provide significant insights into the overall state of security of the Internet, and ZMap made scanning the entire IPv4 address space practical. However, the IPv4 address space is exhausted, and a switch to IPv6, the only accepted long-term solution, is inevitable. In turn, to better understand the security of devices connected to the Internet, including in particular Internet of Things devices, it is imperative to include IPv6 addresses in security evaluations and scans. Unfortunately, it is practically infeasible to iterate through the entire IPv6 address space, as it is 2^96 times larger than the IPv4 address space. Therefore, enumeration of active hosts prior to scanning is necessary. Without it, we will be unable to investigate the overall security of Internet-connected devices in the future. In this paper, we introduce a novel technique to enumerate an active part of the IPv6 address space by walking DNSSEC-signed IPv6 reverse zones. Subsequently, by scanning the enumerated addresses, we uncover significant security problems: the exposure of sensitive data, and incorrectly controlled access to hosts, such as access to routing infrastructure via administrative interfaces, all of which were accessible via IPv6. Furthermore, from our analysis of the differences between accessing dual-stack hosts via IPv6 and IPv4, we hypothesize that the root cause is that machines automatically and by default take on globally routable IPv6 addresses. This is a practice that the affected system administrators appear unaware of, as the respective services are almost always properly protected from unauthorized access via IPv4. Our findings indicate (i) that enumerating active IPv6 hosts is practical without a preferential network position contrary to common belief, (ii) that the security of active IPv6 hosts is currently still lagging behind the security state of IPv4 hosts...
more »
« less
This content will become publicly available on November 13, 2026
A Taxonomy and Comparative Analysis of IPv4 Identifier Selection Correctness, Security, and Performance
The battle for a more secure Internet is waged on many fronts, including the most basic of networking protocols. Our focus is theIPv4 Identifier(IPID), an IPv4 header field as old as the Internet with an equally long history as an exploited side channel for scanning network properties, inferring off-path connections, and poisoning DNS caches. This article taxonomizes the 25-year history of IPID-based exploits and the corresponding changes to IPID selection methods. By mathematically analyzing these methods’ correctness and security and empirically evaluating their performance, we reveal recommendations for best practice as well as shortcomings of current operating system implementations, emphasizing the value of systematic evaluations in network security.
more »
« less
- Award ID(s):
- 2141547
- PAR ID:
- 10649463
- Publisher / Repository:
- ACM
- Date Published:
- Journal Name:
- ACM Computing Surveys
- ISSN:
- 0360-0300
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Internet-wide scanning is a critical tool for security researchers and practitioners alike. By exhaustively exploring the entire IPv4 address space, Internet scanning has driven the development of new security protocols, found and tracked vulnerabilities, improved DDoS defenses, and illuminated global censorship. Unfortunately, the vast scale of the IPv6 address space—340 trillion trillion trillion addresses—precludes exhaustive scanning, necessitating entirely new IPv6-specific scanning methods. As IPv6 adoption continues to grow, developing IPv6 scanning methods is vital for maintaining our capability to comprehensively investigate Internet security. We present 6SENSE, an end-to-end Internet-wide IPv6 scanning system. 6SENSE utilizes reinforcement learning coupled with an online scanner to iteratively reduce the space of possible IPv6 addresses into a tractable scannable subspace, thus discovering new IPv6 Internet hosts. 6SENSE is driven by a set of metrics we identify and define as key for evaluating the generality, diversity, and correctness of IPv6 scanning. We evaluate 6SENSE and prior generative IPv6 discovery methods across these metrics, showing that 6SENSE is able to identify tens of millions of IPv6 hosts, which compared to prior approaches, is up to 3.6x more hosts and 4x more end-site assignments, across a more diverse set of networks. From our analysis, we identify limitations in prior generative approaches that preclude their use for Internet-scale security scans. We also conduct the first Internet-wide scanning-driven security analysis of IPv6 hosts, focusing on TLS certificates unique to IPv6, surveying open ports and security-sensitive services, and identifying potential CVEs.more » « less
-
To mitigate IPv4 exhaustion, IPv6 provides expanded address space, and NAT allows a single public IPv4 address to suffice for many devices assigned private IPv4 address space. Even though NAT has greatly extended the shelf-life of IPv4, some networks need more private IPv4 space than what is officially allocated by IANA due to their size and/or network management practices. Some of these networks resort to using squat space , a term the network operations community uses for large public IPv4 address blocks allocated to organizations but historically never announced to the Internet. While squatting of IP addresses is an open secret, it introduces ethical, legal, and technical problems. In this work we examine billions of traceroutes to identify thousands of organizations squatting. We examine how they are using it and what happened when the US Department of Defense suddenly started announcing what had traditionally been squat space. In addition to shining light on a dirty secret of operational practices, our paper shows that squatting distorts common Internet measurement methodologies, which we argue have to be re-examined to account for squat space.more » « less
-
Since the exhaustion of unallocated IP addresses at the Internet Assigned Numbers Authority (IANA), a market for IPv4 addresses has emerged. In complement to purchasing address space, leasing IP addresses is becoming increasingly popular. Leasing provides a cost-effective alternative for organizations that seek to scale up without a high upfront investment. However, malicious actors also benefit from leasing as it enables them to rapidly cycle through different addresses, circumventing security measures such as IP blocklisting. We explore the emerging IP leasing market and its implications for Internet security. We examine leasing market data, leveraging blocklists as an indirect measure of involvement in various forms of network abuse. In February 2025, leased prefixes were 2.89× more likely to be flagged by blocklists compared to non-leased prefixes. This result raises questions about whether the IP leasing market should be subject to closer scrutiny.more » « less
-
The Domain Name System (DNS) is an essential service for the Internet which maps host names to IP addresses. The DNS Root Sever System operates the top of this namespace. RIPE Atlas observes DNS from more than 11k vantage points (VPs) around the world, reporting the reliability of the DNS Root Server System in DNSmon. DNSmon shows that loss rates for queries to the DNS Root are nearly 10\% for IPv6, much higher than the approximately 2\% loss seen for IPv4. Although IPv6 is ``new,'' as an operational protocol available to a third of Internet users, it ought to be just as reliable as IPv4. We examine this difference at a finer granularity by investigating loss at individual VPs. We confirm that specific VPs are the source of this difference and identify two root causes: VP \emph{islands} with routing problems at the edge which leave them unable to access IPv6 outside their LAN, and VP \emph{peninsulas} which indicate routing problems in the core of the network. These problems account for most of the loss and nearly all of the difference between IPv4 and IPv6 query loss rates. Islands account for most of the loss (half of IPv4 failures and 5/6ths of IPv6 failures), and we suggest these measurement devices should be filtered out to get a more accurate picture of loss rates. Peninsulas account for the main differences between root identifiers, suggesting routing disagreements root operators need to address. We believe that filtering out both of these known problems provides a better measure of underlying network anomalies and loss and will result in more actionable alerts.more » « less
