arXiv subjects

Oliver Gasser

Publications and source records attributed to Oliver Gasser.

At least 37 records · Page 2Linked to original sources

arXiv2023

Exploring the Cookieverse: A Multi-Perspective Analysis of Web Cookies

Web cookies have been the subject of many research studies over the last few years. However, most existing research does not consider multiple crucial perspectives that can influence the cookie landscape, such as the client's location, the impact of cookie banner interaction, and from which operating system a website is being visited. In this paper, we conduct a comprehensive measurement study to analyze the cookie landscape for Tranco top-10k websites from different geographic locations and analyze multiple different perspectives. One important factor which influences cookies is the use of cookie banners. We develop a tool, BannerClick, to automatically detect, accept, and reject cookie banners with an accuracy of 99%, 97%, and 87%, respectively. We find banners to be 56% more prevalent when visiting websites from within the EU region. Moreover, we analyze the effect of banner interaction on different types of cookies (i.e., first-party, third-party, and tracking). For instance, we observe that websites send, on average, 5.5x more third-party cookies after clicking ``accept'', underlining that it is critical to interact with banners when performing Web measurements. Additionally, we analyze statistical consistency, evaluate the widespread deployment of consent management platforms, compare landing to inner pages, and assess the impact of visiting a website on a desktop compared to a mobile phone. Our study highlights that all of these factors substantially impact the cookie landscape, and thus a multi-perspective approach should be taken when performing Web measurement studies.

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arXiv2022

FlowDNS: Correlating Netflow and DNS Streams at Scale

Knowing customer's interests, e.g. which Video-On-Demand (VoD) or Social Network services they are using, helps telecommunication companies with better network planning to enhance the performance exactly where the customer's interests lie, and also offer the customers relevant commercial packages. However, with the increasing deployment of CDNs by different services, identification, and attribution of the traffic on network-layer information alone becomes a challenge: If multiple services are using the same CDN provider, they cannot be easily distinguished based on IP prefixes alone. Therefore, it is crucial to go beyond pure network-layer information for traffic attribution. In this work, we leverage real-time DNS responses gathered by the clients' default DNS resolvers. Having these DNS responses and correlating them with network-layer headers, we are able to translate CDN-hosted domains to the actual services they belong to. We design a correlation system for this purpose and deploy it at a large European ISP. With our system, we can correlate an average of 81.7% of the traffic with the corresponding services, without any loss on our live data streams. Our correlation results also show that 0.5% of the daily traffic contains malformatted, spamming, or phishing domain names. Moreover, ISPs can correlate the results with their BGP information to find more details about the origin and destination of the traffic. We plan to publish our correlation software for other researchers or network operators to use.

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arXiv2022

Illuminating Large-Scale IPv6 Scanning in the Internet

While scans of the IPv4 space are ubiquitous, today little is known about scanning activity in the IPv6 Internet. In this work, we present a longitudinal and detailed empirical study on large-scale IPv6 scanning behavior in the Internet, based on firewall logs captured at some 230,000 hosts of a major Content Distribution Network (CDN). We develop methods to identify IPv6 scans, assess current and past levels of IPv6 scanning activity, and study dominant characteristics of scans, including scanner origins, targeted services, and insights on how scanners find target IPv6 addresses. Where possible, we compare our findings to what can be assessed from publicly available traces. Our work identifies and highlights new challenges to detect scanning activity in the IPv6 Internet, and uncovers that today's scans of the IPv6 space show widely different characteristics when compared to the more well-known IPv4 scans.

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arXiv2022

Deep Dive into the IoT Backend Ecosystem

Internet of Things (IoT) devices are becoming increasingly ubiquitous, e.g., at home, in enterprise environments, and in production lines. To support the advanced functionalities of IoT devices, IoT vendors as well as service and cloud companies operate IoT backends -- the focus of this paper. We propose a methodology to identify and locate them by (a) compiling a list of domains used exclusively by major IoT backend providers and (b) then identifying their server IP addresses. We rely on multiple sources, including IoT backend provider documentation, passive DNS data, and active scanning. For analyzing IoT traffic patterns, we rely on passive network flows from a major European ISP. Our analysis focuses on the top IoT backends and unveils diverse operational strategies -- from operating their own infrastructure to utilizing the public cloud. We find that the majority of the top IoT backend providers are located in multiple locations and countries. Still, a handful are located only in one country, which could raise regulatory scrutiny as the client IoT devices are located in other regions. Indeed, our analysis shows that up to 35% of IoT traffic is exchanged with IoT backend servers located in other continents. We also find that at least six of the top IoT backends rely on other IoT backend providers. We also evaluate if cascading effects among the IoT backend providers are possible in the event of an outage, a misconfiguration, or an attack.

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arXiv2022

Rusty Clusters? Dusting an IPv6 Research Foundation

The long-running IPv6 Hitlist service is an important foundation for IPv6 measurement studies. It helps to overcome infeasible, complete address space scans by collecting valuable, unbiased IPv6 address candidates and regularly testing their responsiveness. However, the Internet itself is a quickly changing ecosystem that can affect longrunning services, potentially inducing biases and obscurities into ongoing data collection means. Frequent analyses but also updates are necessary to enable a valuable service to the community. In this paper, we show that the existing hitlist is highly impacted by the Great Firewall of China, and we offer a cleaned view on the development of responsive addresses. While the accumulated input shows an increasing bias towards some networks, the cleaned set of responsive addresses is well distributed and shows a steady increase. Although it is a best practice to remove aliased prefixes from IPv6 hitlists, we show that this also removes major content delivery networks. More than 98% of all IPv6 addresses announced by Fastly were labeled as aliased and Cloudflare prefixes hosting more than 10M domains were excluded. Depending on the hitlist usage, e.g., higher layer protocol scans, inclusion of addresses from these providers can be valuable. Lastly, we evaluate different new address candidate sources, including target generation algorithms to improve the coverage of the current IPv6 Hitlist. We show that a combination of different methodologies is able to identify 5.6M new, responsive addresses. This accounts for an increase by 174% and combined with the current IPv6 Hitlist, we identify 8.8M responsive addresses.

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arXiv2022

Hyper-Specific Prefixes: Gotta Enjoy the Little Things in Interdomain Routing

Autonomous Systems (ASes) exchange reachability information between each other using BGP -- the de-facto standard inter-AS routing protocol. While IPv4 (IPv6) routes more specific than /24 (/48) are commonly filtered (and hence not propagated), route collectors still observe many of them. In this work, we take a closer look at those "hyper-specific" prefixes (HSPs). In particular, we analyze their prevalence, use cases, and whether operators use them intentionally or accidentally. While their total number increases over time, most HSPs can only be seen by route collector peers. Nonetheless, some HSPs can be seen constantly throughout an entire year and propagate widely. We find that most HSPs represent (internal) routes to peering infrastructure or are related to address block relocations or blackholing. While hundreds of operators intentionally add HSPs to well-known routing databases, we observe that many HSPs are possibly accidentally leaked routes.

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arXiv2022

A Longitudinal View at the Adoption of Multipath TCP

Multipath TCP (MPTCP) extends traditional TCP to enable simultaneous use of multiple connection endpoints at the source and destination. MPTCP has been under active development since its standardization in 2013, and more recently in February 2020, MPTCP was upstreamed to the Linux kernel. In this paper, we provide an in-depth analysis of MPTCPv0 in the Internet and the first analysis of MPTCPv1 to date. We probe the entire IPv4 address space and an IPv6 hitlist to detect MPTCP-enabled systems operational on port 80 and 443. Our scans reveal a steady increase in MPTCPv0-capable IPs, reaching 13k+ on IPv4 (2$\times$ increase in one year) and 1k on IPv6 (40$\times$ increase). MPTCPv1 deployment is comparatively low with $\approx$100 supporting hosts in IPv4 and IPv6, most of which belong to Apple. We also discover a substantial share of seemingly MPTCP-capable hosts, an artifact of middleboxes mirroring TCP options. We conduct targeted HTTP(S) measurements towards select hosts and find that middleboxes can aggressively impact the perceived quality of applications utilizing MPTCP. Finally, we analyze two complementary traffic traces from CAIDA and MAWI to shed light on the real-world usage of MPTCP. We find that while MPTCP usage has increased by a factor of 20 over the past few years, its traffic share is still quite low.

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arXiv2022

SRv6: Is There Anybody Out There?

Segment routing is a modern form of source-based routing, i.e., a routing technique where all or part of the routing decision is predetermined by the source or a hop on the path. Since initial standardization efforts in 2013, segment routing seems to have garnered substantial industry and operator support. Especially segment routing over IPv6 (SRv6) is advertised as having several advantages for easy deployment and flexibility in operations in networks. Many people, however, argue that the deployment of segment routing and SRv6 in particular poses a significant security threat if not done with the utmost care. In this paper we conduct a first empirical analysis of SRv6 deployment in the Internet. First, we analyze SRv6 behavior in an emulation environment and find that different SRv6 implementations have the potential to leak information to the outside. Second, we search for signs of SRv6 deployment in publicly available route collector data, but could not find any traces. Third, we run large-scale traceroute campaigns to investigate possible SRv6 deployments. In this first empirical study on SRv6 we are unable to find traces of SRv6 deployment even for companies that claim to have it deployed in their networks. This lack of leakage might be an indication of good security practices being followed by network operators when deploying SRv6.

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arXiv2022

One Bad Apple Can Spoil Your IPv6 Privacy

IPv6 is being more and more adopted, in part to facilitate the millions of smart devices that have already been installed at home. Unfortunately, we find that the privacy of a substantial fraction of end-users is still at risk, despite the efforts by ISPs and electronic vendors to improve end-user security, e.g., by adopting prefix rotation and IPv6 privacy extensions. By analyzing passive data from a large ISP, we find that around 19% of end-users' privacy can be at risk. When we investigate the root causes, we notice that a single device at home that encodes its MAC address into the IPv6 address can be utilized as a tracking identifier for the entire end-user prefix -- even if other devices use IPv6 privacy extensions. Our results show that IoT devices contribute the most to this privacy leakage and, to a lesser extent, personal computers and mobile devices. To our surprise, some of the most popular IoT manufacturers have not yet adopted privacy extensions that could otherwise mitigate this privacy risk. Finally, we show that third-party providers, e.g., hypergiants, can track up to 17% of subscriber lines in our study.

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arXiv2021

Third Time's Not a Charm: Exploiting SNMPv3 for Router Fingerprinting

In this paper, we show that adoption of the SNMPv3 network management protocol standard offers a unique -- but likely unintended -- opportunity for remotely fingerprinting network infrastructure in the wild. Specifically, by sending unsolicited and unauthenticated SNMPv3 requests, we obtain detailed information about the configuration and status of network devices including vendor, uptime, and the number of restarts. More importantly, the reply contains a persistent and strong identifier that allows for lightweight Internet-scale alias resolution and dual-stack association. By launching active Internet-wide SNMPv3 scan campaigns, we show that our technique can fingerprint more than 4.6 million devices of which around 350k are network routers. Not only is our technique lightweight and accurate, it is complementary to existing alias resolution, dual-stack inference, and device fingerprinting approaches. Our analysis not only provides fresh insights into the router deployment strategies of network operators worldwide, but also highlights potential vulnerabilities of SNMPv3 as currently deployed.

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arXiv2021

From Single Lane to Highways: Analyzing the Adoption of Multipath TCP in the Internet

Multipath TCP (MPTCP) extends traditional TCP to enable simultaneous use of multiple connection endpoints at the source and destination. MPTCP has been under active development since its standardization in 2013, and more recently in February 2020, MPTCP was upstreamed to the Linux kernel. In this paper, we provide the first broad analysis of MPTCPv0 in the Internet. We probe the entire IPv4 address space and an IPv6 hitlist to detect MPTCP-enabled systems operational on port 80 and 443. Our scans reveal a steady increase in MPTCP-capable IPs, reaching 9k+ on IPv4 and a few dozen on IPv6. We also discover a significant share of seemingly MPTCP-capable hosts, an artifact of middleboxes mirroring TCP options. We conduct targeted HTTP(S) measurements towards select hosts and find that middleboxes can aggressively impact the perceived quality of applications utilizing MPTCP. Finally, we analyze two complementary traffic traces from CAIDA and MAWI to shed light on the real-world usage of MPTCP. We find that while MPTCP usage has increased by a factor of 20 over the past few years, its traffic share is still quite low.

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arXiv2021

Zeroing in on Port 0 Traffic in the Wild

Internet services leverage transport protocol port numbers to specify the source and destination application layer protocols. While using port 0 is not allowed in most transport protocols, we see a non-negligible share of traffic using port 0 in the Internet. In this study, we dissect port 0 traffic to infer its possible origins and causes using five complementing flow-level and packet-level datasets. We observe 73 GB of port 0 traffic in one week of IXP traffic, most of which we identify as an artifact of packet fragmentation. In our packet-level datasets, most traffic is originated from a small number of hosts and while most of the packets have no payload, a major fraction of packets containing payload belong to the BitTorrent protocol. Moreover, we find unique traffic patterns commonly seen in scanning. In addition to analyzing passive traces, we also conduct an active measurement campaign to study how different networks react to port 0 traffic. We find an unexpectedly high response rate for TCP port 0 probes in IPv4, with very low response rates with other protocol types. Finally, we will be running continuous port 0 measurements and providing the results to the measurement community.

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arXiv2020

The Lockdown Effect: Implications of the COVID-19 Pandemic on Internet Traffic

Due to the COVID-19 pandemic, many governments imposed lock downs that forced hundreds of millions of citizens to stay at home. The implementation of confinement measures increased Internet traffic demands of residential users, in particular, for remote working, entertainment, commerce, and education, which, as a result, caused traffic shifts in the Internet core. In this paper, using data from a diverse set of vantage points (one ISP, three IXPs, and one metropolitan educational network), we examine the effect of these lockdowns on traffic shifts. We find that the traffic volume increased by 15-20% almost within a week--while overall still modest, this constitutes a large increase within this short time period. However, despite this surge, we observe that the Internet infrastructure is able to handle the new volume, as most traffic shifts occur outside of traditional peak hours. When looking directly at the traffic sources, it turns out that, while hypergiants still contribute a significant fraction of traffic, we see (1) a higher increase in traffic of non-hypergiants, and (2) traffic increases in applications that people use when at home, such as Web conferencing, VPN, and gaming. While many networks see increased traffic demands, in particular, those providing services to residential users, academic networks experience major overall decreases. Yet, in these networks, we can observe substantial increases when considering applications associated to remote working and lecturing.

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arXiv2020

Reserved: Dissecting Internet Traffic on Port 0

Transport protocols use port numbers to allow connection multiplexing on Internet hosts. TCP as well as UDP, the two most widely used transport protocols, have limitations on what constitutes a valid and invalid port number. One example of an invalid port number for these protocols is port 0. In this work, we present preliminary results from analyzing port 0 traffic at a large European IXP. In one week of traffic we find 74GB port 0 traffic. The vast majority of this traffic has both source and destination ports set to 0, suggesting scanning or reconnaissance as its root cause. Our analysis also shows that more than half of all port 0 traffic is targeted to just 18 ASes, whereas more than half of all traffic is originated by about 100 ASes, suggesting a more diverse set of source ASes.

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arXiv2018

Clusters in the Expanse: Understanding and Unbiasing IPv6 Hitlists

Network measurements are an important tool in understanding the Internet. Due to the expanse of the IPv6 address space, exhaustive scans as in IPv4 are not possible for IPv6. In recent years, several studies have proposed the use of target lists of IPv6 addresses, called IPv6 hitlists. In this paper, we show that addresses in IPv6 hitlists are heavily clustered. We present novel techniques that allow IPv6 hitlists to be pushed from quantity to quality. We perform a longitudinal active measurement study over 6 months, targeting more than 50 M addresses. We develop a rigorous method to detect aliased prefixes, which identifies 1.5 % of our prefixes as aliased, pertaining to about half of our target addresses. Using entropy clustering, we group the entire hitlist into just 6 distinct addressing schemes. Furthermore, we perform client measurements by leveraging crowdsourcing. To encourage reproducibility in network measurement research and to serve as a starting point for future IPv6 studies, we publish source code, analysis tools, and data.

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arXiv2018

The Rise of Certificate Transparency and Its Implications on the Internet Ecosystem

In this paper, we analyze the evolution of Certificate Transparency (CT) over time and explore the implications of exposing certificate DNS names from the perspective of security and privacy. We find that certificates in CT logs have seen exponential growth. Website support for CT has also constantly increased, with now 33% of established connections supporting CT. With the increasing deployment of CT, there are also concerns of information leakage due to all certificates being visible in CT logs. To understand this threat, we introduce a CT honeypot and show that data from CT logs is being used to identify targets for scanning campaigns only minutes after certificate issuance. We present and evaluate a methodology to learn and validate new subdomains from the vast number of domains extracted from CT logged certificates.

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arXiv2017

HLOC: Hints-Based Geolocation Leveraging Multiple Measurement Frameworks

Geographically locating an IP address is of interest for many purposes. There are two major ways to obtain the location of an IP address: querying commercial databases or conducting latency measurements. For structural Internet nodes, such as routers, commercial databases are limited by low accuracy, while current measurement-based approaches overwhelm users with setup overhead and scalability issues. In this work we present our system HLOC, aiming to combine the ease of database use with the accuracy of latency measurements. We evaluate HLOC on a comprehensive router data set of 1.4M IPv4 and 183k IPv6 routers. HLOC first extracts location hints from rDNS names, and then conducts multi-tier latency measurements. Configuration complexity is minimized by using publicly available large-scale measurement frameworks such as RIPE Atlas. Using this measurement, we can confirm or disprove the location hints found in domain names. We publicly release HLOC's ready-to-use source code, enabling researchers to easily increase geolocation accuracy with minimum overhead.

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arXiv2017

Large-Scale Classification of IPv6-IPv4 Siblings with Variable Clock Skew

Linking the growing IPv6 deployment to existing IPv4 addresses is an interesting field of research, be it for network forensics, structural analysis, or reconnaissance. In this work, we focus on classifying pairs of server IPv6 and IPv4 addresses as siblings, i.e., running on the same machine. Our methodology leverages active measurements of TCP timestamps and other network characteristics, which we measure against a diverse ground truth of 682 hosts. We define and extract a set of features, including estimation of variable (opposed to constant) remote clock skew. On these features, we train a manually crafted algorithm as well as a machine-learned decision tree. By conducting several measurement runs and training in cross-validation rounds, we aim to create models that generalize well and do not overfit our training data. We find both models to exceed 99% precision in train and test performance. We validate scalability by classifying 149k siblings in a large-scale measurement of 371k sibling candidates. We argue that this methodology, thoroughly cross-validated and likely to generalize well, can aid comparative studies of IPv6 and IPv4 behavior in the Internet. Striving for applicability and replicability, we release ready-to-use source code and raw data from our study.

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