CN116074022A - Automatic lateral movement identification method based on process control and artificial intelligence - Google Patents

Abstract

The invention discloses a method for automatically identifying transverse movement based on process control and artificial intelligence, which is characterized in that malicious RDP session can be automatically detected, and each network attack can go through a plurality of stages before being terminated. Lateral movement is one of the particularly important phases, and remote desktop protocol RDP is a major tool used by lateral movement for successfully authenticating identity to an unauthorized host, which host has a footprint on both the host and Windows event log, and for identifying whether an RDP session is malicious by applying a machine learning model to the RDP session in the Windows event log, and the method further comprises the steps of: the method comprises the steps of (1) extracting features, (2) preprocessing, (3) detecting malicious RDP session based on Logitoost algorithm, (4) detecting malicious RDP session, and (5) performing network attack in a lateral movement stage. The invention can detect the transverse movement Cheng Guankong so as to realize early warning of network attack.

Description

Automatic lateral movement identification method based on process control and artificial intelligence

Technical Field

The invention relates to the technical fields of network security, SOC (Security operation center), process control, artificial intelligence and transverse movement, in particular to a method for automatically identifying transverse movement based on process control and artificial intelligence.

Background

Existing security threat detection methods assume that the intrusion is successful and focus on a single event. However, in recent network attacks, particularly complex attacks, the campaign of a single attack by a single hacker is often composed of a plurality of smaller, imperceptible attacks. Detecting these attacks can be challenging because a campaign may develop over time, including multiple phases, each of which is intended to defeat the defenses and occur at a different time.

All attacks that occur in the network space have a pattern that can be described as a series of events that can be divided into different phases, also called a process control model (as shown in fig. 1). Network attacks begin by detecting and identifying targets in the network. Then the weaponized payload is manufactured. The weaponization of payloads typically takes the form of malicious emails and attachments that are sent to the target machines of interest. The attack begins after delivery, after which malicious code is triggered. While malicious code may execute independently, some malware attacks with applications on the target machine. This may include operating system based BUGs (e.g., in RDP and PsExec) to application based BUGs (e.g., in real-time processes such as in Google Chrome and Microsoft Office). The attacker then proceeds to install a secure backdoor on the system or activate a system-built-in function (e.g., RDP), allowing an external persistent connection. After establishing the persistent connection, the attacker may begin performing different operations as it moves laterally in the environment. These operations leave system logs on the target machine and utilize these logs in the detection of lateral mobile attacks.

Most security systems maintain a strong boundary (e.g., firewall, intrusion prevention system) between the internet and the intranet, and an attacker, while being able to choose to access its back target host, has difficulty in launching an attack on the asset residing in the intranet. Thus, attackers often use social engineering techniques (e.g., fishing, baiting, etc.) to decoy network internals to execute malicious code or to submit credentials. This enables an attacker to access the victim's computer and progressively explore valuable information by exploiting vulnerabilities of other intranet entities. This is commonly referred to as lateral movement (Lateral Movement LM).

In the process control model, lateral movement is considered an important network attack behaviour. Lateral movement includes stealing credentials and penetrating into other machines controlled by the attacker to move laterally in the network and gain higher authority to achieve the attacker's goal.

In the lateral movement phase, attackers tend to use legitimate system tools, which makes detection of network attacks a challenging task. However, machine learning (Machine Learning ML) techniques have been widely used in the detection of complex network attacks. Machine learning is an ideal tool for extracting knowledge from data and learning system behaviors, and is an artificial intelligence method.

Advanced persistent threats (Advanced Persistent Threat APT) are typical representatives of the most prominent complex network attacks, with the potential for significant damage to various organizations and businesses. This is a type of covert attack where an attacker has unauthorized access to the network for a long period of time. A backdoor procedure called Carbanak has been reported to cause a dollar loss to a financial institution of 10 billion. In addition, over 8000 ten thousand social security numbers were stolen from the large health insurance company, anthem, which was discovered only after 9 months.

APT detection methods typically rely on network traffic data or host system logs to discover evidence of APT. Network-based intrusion detection has been well explored, but has several drawbacks. First, the information that can be extracted from the network data is limited. For privacy reasons, it is important to extract meaningful information beyond packet statistics and basic quintuples (i.e., source IP, destination IP, source port, destination port, and protocol) without user consent to check the network payload for illegitimate. In addition, more recently 72% of network traffic is encrypted using protocols such as Transport Layer Security (TLS). This makes it challenging to inspect the payload of a packet without significantly degrading system performance. Furthermore, attackers that initiate APT tend to be cautious and often utilize custom protocols, making it more difficult to detect abnormal behavior in network data.

On the other hand, host-based intrusion detection may overcome the limitations described above. At the end host, the data is decrypted, allowing information to be extracted, including payload entropy, packet loss rate, and login failure, which may improve detection performance. In addition, the operating system has a built-in log function and can provide rich information. By enabling or disabling different logging levels and policies, only useful information can be logged. There are multiple stages in APT, some of which leave a footprint to detect intrusion at an early stage. For example, an intruder may access a target host in the intranet, but this operation will generate a suspicious log on the end host.

The remote desktop protocol (Remote Desktop Protocol RDP) is designed by Microsoft to provide remote display and input functionality, while the remote desktop service (Remote Desktop Service RDS) is a native service implementing RDP on the Microsoft Windows platform. Legal network administrators often use this service. However, it is also the main tool used by an attacker during the lateral movement phase, as it is challenging to distinguish between legitimate or malicious uses of the tool.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for automatically identifying the transverse movement based on process control and artificial intelligence, which adopts a LogitBoost algorithm and Windows RDP event logs to detect the evidence of the transverse movement so as to realize early warning of network attack.

The method for automatically identifying the transverse movement based on the process control and the artificial intelligence is characterized by automatically detecting malicious RDP sessions, wherein each network attack can go through a plurality of stages before being terminated. Lateral movement is one of the particularly important phases, and remote desktop protocol RDP is a major tool used by lateral movement for successfully authenticating identity to an unauthorized host, which host has a footprint on both the host and Windows event log, and for identifying whether an RDP session is malicious by applying a machine learning model to the RDP session in the Windows event log, and the method further comprises the steps of:

(1) Extracting features, including the following features:

user (Usr) User name for RDP identity authentication;

source (Src) Source host initiating RDP identity authentication;

destination (Dst) RDP identity authentication target host;

session duration: duration of RDP Session (seconds);

user time difference include user Usr _i Is a two-continuous RDP authentication event e _j And e _k Is a time difference of (2);

source time difference it contains source host Src _i Is a two-continuous RDP authentication event e _j And e _k Is a time difference of (2);

destination time difference include target host Dst _i Is a two-continuous RDP authentication event e _j And e _k Is a time difference of (2);

mean of session duration for user include user Usr _i Average duration of all RDP sessions;

mean of session duration for source it contains source host Src _i Average duration of all RDP sessions;

mean of session duration for destination include target host Dst _i Average duration of all RDP sessions;

weekday, the workday extracted from the timestamp;

second in a day, time of day (Seconds);

(2) Preprocessing, discarding RDP session events such as short time;

(3) Applying a LogitBoost algorithm to the RDP session in the Windows event log;

(4) Detecting a malicious RDP session;

(5) The network attack is in a lateral mobile phase.

Further, the Logitboost algorithm, (x ₁ ，y ₁ )，…，(x _N ，y _N ) Training data for the algorithm, where x _i As a feature vector, y _i = -1 or y _i =1, representing malicious or benign RDP sessions, weight

And probability estimation +.>

The following steps are repeated for m=1, 2,3, … M:

(1) Calculating job response and weight:

w _i ＝p(x _i )(1-p(x _i ))；

(2) By using weights w _i Z of (2) _i To x _i Least mean square regression of weights of (2) to fit a function f _m (x)；

(3) Updating

And->

(4) Output classification

The invention has the technical effects that:

in the present invention, a method for automatically identifying lateral movement based on process control and artificial intelligence is provided, which is characterized in that malicious RDP sessions can be automatically detected, and each network attack can go through several stages before being terminated. Lateral movement is one of the particularly important phases, and remote desktop protocol RDP is a major tool used by lateral movement for successfully authenticating identity to an unauthorized host, which host has a footprint on both the host and Windows event log, and for identifying whether an RDP session is malicious by applying a machine learning model to the RDP session in the Windows event log, and the method further comprises the steps of: the method comprises the steps of (1) extracting features, (2) preprocessing, (3) detecting malicious RDP session based on Logitoost algorithm, (4) detecting malicious RDP session, and (5) performing network attack in a lateral movement stage. The invention can detect the transverse movement Cheng Guankong so as to realize early warning of network attack.

Drawings

FIG. 1 is a process control schematic of a method for automatically identifying lateral movement based on process control and artificial intelligence;

FIG. 2 is a lateral movement schematic diagram of a method of automatically identifying lateral movement based on process control and artificial intelligence;

FIG. 3 is a schematic diagram of a Windows event log field of a method for automatically identifying lateral movement based on process control and artificial intelligence;

FIG. 4 is a schematic diagram of a method of automatically identifying lateral movement based on process control and artificial intelligence.

Detailed Description

The invention is described in further detail below, with reference to the attached drawings and examples:

FIG. 1 is a process control schematic of a method for automatically identifying lateral movement based on process control and artificial intelligence. The process control comprises three stages; further, the process control includes: a reconnaissance stage, a delivery stage, an installation stage, a right lifting stage, a transverse movement stage, an operation target stage and a withdrawal stage; the three stages are specifically described as follows:

the first stage: the network stage (including reconnaissance stage and delivery stage) is that the enterprise network system operates normally without any invasion; at this stage, a hacker or attacker would employ, for example, a phishing attack to scout the target network; the application provides an anti-reconnaissance technology for detecting the phishing attack.

And a second stage: the endpoint phase (including the installation phase, the rights promotion phase) from which the system is always compromised, the attacker is within the enterprise network, but does not have complete control of the enterprise network.

And a third stage: domain phase or evacuation phase (including lateral movement phase, operation target phase and evacuation phase), attacker can raise authority and control machine completely, and attacker can delete and manipulate log so as to make attack trace disappear.

For the scout phase, an attacker is involved actively or passively collecting information that can be used to support target localization. Such information may include detailed information of the victim's enterprise, critical infrastructure, or staff. The attacker can use this information to assist in other phases of the attacker's lifecycle, such as planning and performing deliveries using the collected information, determining the scope and priority of targets after intrusion, or pushing and leading further scouting work.

FIG. 2 is a lateral movement schematic diagram of a method for automatically identifying lateral movement based on process control and artificial intelligence. In fig. 2, a machine residing in an enterprise network (i.e., host 1) is destroyed by an attacker through social engineering (e.g., phishing). Suppose that there was previously an RDP connection from host 1 to host 2, the credentials for accessing host 2 were cached on host 1. In this case, an attacker may perform credential stealing on host 1 to gain access to another internal host (i.e. laterally moved to host 2) with physical access to the database. Note that these databases are not directly connected to the Internet. The attacker may then attempt to connect to the internal database using the stolen credentials of another internal host. In fact, hackers are less likely to successfully initiate an intrusion without lateral movement, as key assets are typically not directly accessible from outside the network. Thus, the use of lateral movement also facilitates detection of early attacks. The present application provides solutions for lateral movement detection based on host-based RDP evidence.

FIG. 3 is a schematic diagram of Windows event log fields of a method of automatically identifying lateral movement based on process control and artificial intelligence. Collecting Windows event logs, while simple, requires defining the type of system objects to be monitored (e.g., files or registry entries, network events), the type of access to these objects (read, write, rights change, etc.) should be recorded, and which accesses (user, system, all, etc.) should be monitored. The configuration of this information is maintained in three locations: i) A secure access control list (security access control list SACL) that controls the audit access types of all files and registry objects; ii) a local security policy that controls which types of objects and events generate events in the log; and iii) a Windows firewall that in part controls the logging of network specific events (e.g., network connections). Using domain controllers, specific policies can be easily applied to the entire enterprise network.

While opening all logging mechanisms can maximize coverage of possible behaviors, the number of logging events quickly exceeds the commodity storage system and significantly affects the performance of the monitored computer. To filter out most of these events while maintaining their utility in detecting malicious behavior, "read-only" events have been deleted from the collection, as almost all malicious behavior involves some form of modification to the system (reconnaissance is a significant exception). In summary, only the writing, deletion and execution of files/registries, and process generation are ultimately recorded. In addition, windows event IDs associated with the collection of data of the present application are 4624 (indicating that an account has been successfully logged in), 4625 (indicating that an account has failed to log in), and 4634 (indicating that an account has been logged out), which are associated with RDP identity authentication.

As can be seen from FIG. 3, a logo type of 10 in the computer Windows event log indicates that RDP is used for telnet, which is very useful for tracking malicious RDP sessions of the present application.

FIG. 4 is a schematic diagram of a method of automatically identifying lateral movement based on process control and artificial intelligence. The method comprises the following steps:

1. extracting features, including the following features:

user (Usr) User name for RDP identity authentication;

source (Src) Source host initiating RDP identity authentication;

destination (Dst) RDP identity authentication target host;

session duration: duration of RDP Session (seconds);

user time difference include user Usr _i Is to be used for two continuous RDP identity authentication eventsPiece e _j And e _k Is a time difference of (2);

source time difference it contains source host Src _i Is a two-continuous RDP authentication event e _j And e _k Is a time difference of (2);

destination time difference include target host Dst _i Is a two-continuous RDP authentication event e _j And e _k Is a time difference of (2);

mean of session duration for user include user Usr _i Average duration of all RDP sessions;

mean of session duration for source it contains source host Src _i Average duration of all RDP sessions;

mean of session duration for destination include target host Dst _i Average duration of all RDP sessions;

weekday, the workday extracted from the timestamp;

second in a day, time of day (Seconds).

It should be noted that not all attributes in the original dataset are used to extract the features described above. The functions of event ID, process name, process ID, login type description, and domain name have the same value in all events. Thus, they are deleted from the function list. The login ID is only used to calculate the session duration.

2. Pretreatment of

An event log of authentication type 10 is collected for Windows event ID 4624 (indicating that an account has been successfully logged in), 4625 (indicating that an account has failed to log in), and 4634 (indicating that an account has been logged out). Event logs lacking the source host are discarded, and the data sets of invalid data items and RDP session events of very short session length are purged.

In addition, the attacker's authentication event contains only the login event (ID 4634), and does not contain the logoff event (ID 4634). Thus, this may prevent the calculation of malicious RDP session duration. To this end, session duration is generated for each aggressor event according to a normal distribution

Where μ and σ are the mean and standard deviation, respectively, calculated from the durations of all benign RDP sessions. Although a random distribution may be more reasonable, since the attack may last any time, it is assumed that the attack has a similar behavior (session time) as a benign user. This assumption makes classification more difficult because the malicious data points are closer to the benign data points in this feature. It also makes the data more realistic, as some attackers may simulate benign activities to avoid detection.

3. The Logitoost algorithm comprises the following steps:

1、(x ₁ ，y ₁ )，…，(x _N ，y _N ) Training data for the algorithm, where x _i As a feature vector, y _i = -1 or y _i =1, representing malicious or benign RDP sessions;

2. weighting of

And probability estimation +.>

3. The following steps are repeated for m=1, 2,3, … M:

(1) Calculating job response and weight:

w _i ＝p(x _i )(1-p(x _i ))。

(2) By using weights w _i Z of (2) _i To x _i Least mean square regression of weights of (2) to fit a function f _m (x)。

(3) Updating

And->

(4) Output classification

4. Malicious RDP sessions

Based on the LogitBoost algorithm, malicious RDP sessions are detected.

5. Stage of lateral movement

Network attacks are in the lateral mobile phase, malicious RDP sessions are often used by attackers to implement remote attacks in the lateral mobile phase.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention; all changes and modifications that come within the meaning and range of equivalency of the invention are to be embraced within their scope.

Claims (2)

1. The method is characterized in that a malicious RDP session can be automatically detected, each network attack can go through several stages before being terminated, the lateral movement is one of the particularly important stages, the remote desktop protocol RDP is a main tool used for the lateral movement and is used for successfully carrying out identity authentication on an unauthorized host, the host can leave footprints on the host and Windows event logs, and whether the RDP session is malicious or not is identified by applying a machine learning model to the RDP session in the Windows event logs, and the method further comprises the following steps:

(1) Extracting features, including the following features:

user (Usr) User name for RDP identity authentication;

source (Src) Source host initiating RDP identity authentication;

destination (Dst) RDP identity authentication target host;

session duration: duration of RDP Session (seconds);

user time difference include user

Two consecutive RDP authentication events +.>

And->

Is a time difference of (2);

source time difference include source host

Is +.>

And->

Is a time difference of (2);

destination time difference it contains target host

Is +.>

And

is a time difference of (2);

mean of session duration for user include user

Average duration of all RDP sessions;

mean of session duration for source include source host

Average duration of all RDP sessions;

mean of session duration for destination it contains target host

Average duration of all RDP sessions;

weekday, the workday extracted from the timestamp;

second in a day, time of day (Seconds);

(2) Preprocessing, discarding RDP session events such as short time;

(3) Applying a LogitBoost algorithm to the RDP session in the Windows event log;

(4) Detecting a malicious RDP session;

(5) The network attack is in a lateral mobile phase.

2. The process control and artificial intelligence based method for automatically identifying lateral movement of claim 1, wherein the LogitBoost algorithm @ is

，/>

），…，（/>

，/>

) Training data for the algorithm, wherein +.>

Is a feature vector +_>

= -1 or->

=1, indicating malicious or benign RDP session, weight ++>

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I=1, 2, …, N, F (x) =0, and probability estimation p (++>

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The following steps are repeated for m=1, 2,3, … M:

(1) Calculating job response and weight:

=/>

，/>

=p(/>

)（1- p(/>

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(2) By using weights

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Least mean square regression of weights of (2) to fit a function +.>

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(3) Update F (x)

F(x)+/>

And p (x) = =>

；

(4) Output classification sign [ F (x)]= sign[

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Images