Investors and regulators can greatly benefit from a realistic market simulator that enables them to anticipate the consequences of their decisions in real markets. However, traditional rule-based market simulators often fall short in accurately capturing the dynamic behavior of market participants, particularly in response to external market impact events or changes in the behavior of other participants. In this study, we explore an agent-based simulation framework employing reinforcement learning (RL) agents. We present the implementation details of these RL agents and demonstrate that the simulated market exhibits realistic stylized facts observed in real-world markets. Furthermore, we investigate the behavior of RL agents when confronted with external market impacts, such as a flash crash. Our findings shed light on the effectiveness and adaptability of RL-based agents within the simulation, offering insights into their response to significant market events.

The DNS Security Extensions (DNSSEC) add authenticity and integrity to the naming system of the Internet. Resolvers that validate information in the DNS need to know the cryptographic public key used to sign the root zone of the DNS. Eight years after its introduction and one year after the originally scheduled date, this key was replaced by ICANN for the first time in October 2018. ICANN considered this event, called a rollover, "an overwhelming success" and during the rollover they detected "no significant outages". In this paper, we independently follow the process of the rollover starting from the events that led to its postponement in 2017 until the removal of the old key in 2019. We collected data from multiple vantage points in the DNS ecosystem for the entire duration of the rollover process. Using this data, we study key events of the rollover. These events include telemetry signals that led to the rollover being postponed, a near real-time view of the actual rollover in resolvers and a significant increase in queries to the root of the DNS once the old key was revoked. Our analysis contributes significantly to identifying the causes of challenges observed during the rollover. We show that while from an end-user perspective, the roll indeed passed without major problems, there are many opportunities for improvement and important lessons to be learned from events that occurred over the entire duration of the rollover. Based on these lessons, we propose improvements to the process for future rollovers.

The recent unprecedented delegation of new generic top-level domains (gTLDs) has exacerbated an existing, but fallow, problem called name collisions. One concrete exploit of such problem was discovered recently, which targets internal namespaces and enables Man in the Middle (MitM) attacks against end-user devices from anywhere on the Internet. Analysis of the underlying problem shows that it is not specific to any single service protocol, but little attention has been paid to understand the vulnerability status and the defense solution space at the service level. In this paper, we perform the first systematic study of the robustness of internal network services under name collision attacks.

Recently, Man in the Middle (MitM) attacks on web browsing have become easier than they have ever been before because of a problem called "Name Collision" and a protocol called the Web Proxy Auto-Discovery (WPAD) protocol. This name collision attack can cause all web traffic of an Internet user to be redirected to a MitM proxy automatically right after the launching of a standard browser. The underlying problem of this attack is internal namespace WPAD query leakage, which itself is a known problem for years. However, it remains understudied since it was not easily exploitable before the recent new gTLD (generic Top-Level Domains) delegation. In this paper, we focus on this newly-exposed MitM attack vector and perform the first systematic study of the underlying problem causes and its vulnerability status in the wild. First, we show the severity of the problem by characterizing leaked WPAD query traffic to the DNS root servers, and find that a major cause of the leakage problem is actually a result of settings on the end user devices. More specifically, we find that under common settings, devices can mistakenly generate internal queries when used outside an internal network (e.g., used at home). Second, we define and quantify a candidate measure of attack surface by defining "highly-vulnerable domains", which are domains routinely exposing a large number of potential victims, and use it to perform a systematic assessment of the vulnerability status. We find that almost all leaked queries are for new gTLD domains we define to be highly-vulnerable, indirectly validating our attack surface definition. We further find that 10% of these highly-vulnerable domains have already been registered, making the corresponding users immediately vulnerable to the exploit at any time. Our results provide a strong and urgent message to deploy proactive protection. We discuss promising directions for remediation at the new gTLD registry, Autonomous System (AS), and end user levels, and use empirical data analysis to estimate and compare their effectiveness and deployment difficulties.

Spammers register a tremendous number of domains to evade blacklisting and takedown efforts. Current techniques to detect such domains rely on crawling spam URLs or monitoring lookup traffic. Such detection techniques are only effective after the spammers have already launched their campaigns, and thus these countermeasures may only come into play after the spammer has already reaped significant benefits from the dissemination of large volumes of spam. In this paper we examine the registration process of such domains, with a particular eye towards features that might indicate that a given domain likely has a malicious purpose at registration time, before it is ever used for an attack. Our assessment includes exploring the characteristics of registrars, domain life cycles, registration bursts, and naming patterns. By investigating zone changes from the .com TLD over a 5-month period, we discover that spammers employ bulk registration, that they often re-use domains previously registered by others, and that they tend to register and host their domains over a small set of registrars. Our findings suggest steps that registries or registrars could use to frustrate the efforts of miscreants to acquire domains in bulk, ultimately reducing their agility for mounting large-scale attacks.