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You Get What You Sample: Evaluating Sampling Strategies for Web Security Measurements
Evaluation of 500k Tranco and 24.8M Common Crawl hosts shows Top-N domain sampling biases web security measurements; probability sampling yields unbiased estimates.
The study is the first comprehensive investigation of how sampling strategies affect web security measurement conclusions, comparing datasets and strategies across 500k Tranco domains and 24.8M Common Crawl hosts. It shows Top-N selection does not reflect the overall web distribution and may bias observed vulnerability rates, while probability-based strategies yield stable, unbiased prevalence and impact estimates. Hybrid sampling offers no advantage because its deterministic prefix consistently hurts accuracy, and the authors propose an adaptive probability-based strategy effective even when target prevalence is unknown.
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Recent Trends in Internet Threats: Common Industries Impersonated in Phishing Attacks, Web Skimmer Analysis and More
Unit 42 analyzed 67 million malicious URLs and domains in H2 2022, a 52% increase, highlighting phishing impersonation and web skimmer trends.
Unit 42 observed more than 67 million unique malicious URLs, domains and IPs between July and December 2022, a 52% increase over the first half of the year. Malicious JavaScript detections grew 99.3%, with over 4 million malicious JS samples hosted on 4.8 million URLs. Over 85% of hosting infrastructure was concentrated in eight countries, led by the United States, Brazil and China. The report also analyzes industries spoofed in phishing pages and includes a web skimmer case study on a Tranco top 1 million website.
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ApateWeb: An Evasive Large-Scale Scareware and PUP Delivery Campaign
Unit 42 uncovers ApateWeb, a campaign using over 130,000 domains and multilayered redirects to deliver scareware, adware and PUPs to millions of users.
Unit 42 discovered ApateWeb, a large-scale campaign using a network of more than 130,000 domains to deliver scareware, potentially unwanted programs, adware including a rogue browser and browser extensions, and scam pages. The campaign uses a three-layer structure with deceptive emails as the entry point, centralized victim tracking via UUIDs, intermediate adware or anti-bot redirections, and evasion tactics such as cloaking, bot detection error pages, and wildcard DNS abuse. Activity spiked since August 2022, with several hundred attacker-controlled sites remaining in Tranco's top 1 million rankings and millions of monthly hits; Unit 42 blocked an estimated 3.5 million sessions across 74,711 devices in November 2023.
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Evaluating Practical Enumeration and Blocking Attacks on the Snowflake Circumvention System
Ethical measurements enumerated 21,000+ Snowflake proxy IPs across ~1,000 ASes; blocking top 1% of ASes disrupts 30% of Snowflakes.
Researchers tested Snowflake's assumptions that proxy IPs cannot be easily enumerated and that blocking them causes unacceptable collateral damage. Over 48 days of real-world measurements (May-June 2025), malicious-client-style enumeration collected over 21,000 unique proxy IPs across almost 1,000 autonomous systems. Blocking the top 1% of ASes blocks more than 30% of observed Snowflakes while affecting about 2.5% of Tranco Top 1M domains, and the broker's load-aware matching leaks stable high-capacity proxies to attackers. Some proposed mitigations have already been integrated into Snowflake.
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CDN Tsunami Attack Abuses HTTP/3 Translation for Up to 350x DoS Amplification
Researchers disclosed two DoS attacks exploiting CDNs' HTTP/3-to-HTTP/1.1 translation to amplify low-bandwidth requests up to 350x against origin servers.
Researchers named the two techniques HTTP/3 Bandwidth Amplification (HBA) and HTTP/3 Connection Amplification (HCA), exploiting the gap where CDNs speak HTTP/3 to browsers but only HTTP/1.1 to origins. All six tested CDNs (Alibaba, Baidu, Cloudflare, CloudFront, Fastly, Tencent) were susceptible to HBA, and five to HCA, with Cloudflare immune to HCA because it buffers full requests before opening backend connections. Attackers using under 5 Mbps forced over 100 Mbps at origins, and the 350x factor applies only to Alibaba, Baidu, and Tencent, which support the QPACK dynamic table. Testing identified 42,330 potentially vulnerable subdomains out of 151,685 hosted on the six providers across the Tranco Top 1M.
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TLD Tracker: Exploring Newly Released Top
Unit 42 tracked 19 newly released top-level domains and found large-scale phishing, unwanted program distribution, and cybersquatting tied to TLD launch dates.
Researchers analyzed 19 new generic TLDs, including .zip, .bot, .ing, and .meme, released or approaching general availability over roughly 18 months. Data from passive DNS, registry zone files, newly registered domain feeds, and the Tranco top-1M list showed phishing campaigns, potentially unwanted program distribution, and domain squatting on these TLDs. Abuse correlated with each TLD's rollout phases, indicating attackers monitor general availability dates to register and weaponize domains. The IANA root database now lists over 1,000 generic TLDs.
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