Modeling and detection of the multistages of Advanced Persistent Threats attacks based on semisupervised learning and complex networks characteristics Abstract   Advanced Persistent Threats (APT) present the most sophisticated types of attacks to modern networks which have proved to be very challenging to address. Using sophisticated attack techniques, attackers remotely control infected machines and exfiltrate sensitive information from organizations and governments. Security products deployed by enterprise networks based on traditional defenses often fail at detecting APT infections because of the dynamic nature of the APT attack process. To overcome the current limitations of attack network dynamics faced in APT studies, an innovative APT attack detection model based on a semisupervised learning approach and complex networks characteristics is proposed in this paper. The entire targeted network is modeled as a smallworld network and the evolving APTAttack Network (APTAN) as a scalefree network. Finite state machines are employed to model the state transitions of the nodes in the time domain in order to characterize the state changes during the APT attack process. The effectiveness of the model is demonstrated by applying it to realworld data from a largescale enterprise network consisting of 17,684 hosts from the Los Alamos security lab. The proposed approach analyzes efficiently the largescale dataset to reveal APT attack characteristics between the command and control center and the victim hosts. The final result is a ranked list of suspicious hosts participating in APT attack activities. The average detection precision of three APT stage is 90.5% in our proposed APT detection framework. The results show that the model can effectively detect the suspicious hosts at different stages of the APT attack process.

Discovering Suspicious APT Behaviors by Analyzing DNS Activities As sensors become more prevalent in our lives, security issues have become a major concern. In the Advanced Persistent Threat (APT) attack, the sensor has also become an important role as a transmission medium. As a relatively weak link in the network transmission process, sensor networks often become the target of attackers. Due to the characteristics of low traffic, long attack time, diverse attack methods, and realtime evolution, existing detection methods have not been able to detect them comprehensively. Current research suggests that a suspicious domain name can be obtained by analyzing the domain name resolution (DNS) request to the target network in an APT attack. In past work based on DNS log analyses, most of the work would simply calculate the characteristics of the request message or the characteristics of the response message or the feature set of the request message plus the response message, and the relationship between the response message and the request message was not considered. This may leave out the detection of some APT attacks in which the DNS resolution process is incomplete. This paper proposes a new feature that represents the relationship between a DNS request and the response message, based on a deep learning method used to analyze the DNS request records. The algorithm performs threat assessment on the DNS behavior to be detected based on the calculated suspicious value. This paper uses the data of 4, 907, 147, 146 DNS request records (376, 605, 606 records after DNS Data Preprocessing) collected in a large campus network and uses simulation attack data to verify the validity and correctness of the system. The results of the experiments show that our method achieves an average accuracy of 97.6% in detecting suspicious DNS behavior, with the orange false positive (FP) at 2.3% and the recall at 96.8%. The proposed system can effectively detect the hidden and suspicious DNS behavior in APT.