The cybersecurity community has made substantial efforts to understand and mitigate security flaws in information systems. Oftentimes when a compromise is discovered, it is difficult to identify the actions performed by an attacker.

In this study, we explore the compromise phase, i.e., when an attacker exploits the host he/she gained access to using a vulnerability exposed by an information system. More specifically, we look at the main actions performed during the compromise and the factors deterring the attackers from exploiting the compromised systems.

Because of the lack of security datasets on compromised systems, we need to deploy systems to more adequately study attackers and the different techniques they employ to compromise computer. Security researchers employ target computers, called honeypots, that are not used by normal or authorized users.

In this study we first describe the distributed honeypot network architecture deployed at the University of Maryland and the different honeypot-based experiments enabling the data collection required to conduct the studies on attackers' behavior.

In a first experiment we explore the attackers' skill levels and the purpose of the malicious software installed on the honeypots. We determined the relative skill levels of the attackers and classified the different software installed.

We then focused on the crimes committed by the attackers, i.e., the attacks launched from the honeypots by the attackers. We defined the different computer crimes observed (e.g., brute-force attacks and denial of service attacks) and their characteristics (whether they were coordinated and/or destructive). We looked at the impact of computer resources restrictions on the crimes and then, at the deterrent effect of warning and surveillance. Lastly, we used different metrics related to the attack sessions to investigate the impact of surveillance on the attackers based on their country of origin.

During attacks, we found that attackers mainly installed IRC-based bot tools and sometimes shared their honeypot access. From the analysis on crimes, it appears that deterrence does not work; we showed attackers seem to favor certain computer resources. Lastly, we observed that the presence of surveillance had no significant impact on the attack sessions, however surveillance altered the behavior originating from a few countries.