If you’re planning to take the SY0-501 version of the Security+ exam, you should have a basic understanding of some specific tools used to assess networks and manage risks. This includes using a centralized solution for collecting, analyzing, and managing data from multiple sources.
For example, can you answer this question?
Q. An organization has a large network with dozens of servers. Administrators are finding it difficult to review and analyze the logs from all the network devices. They are looking for a solution to aggregate and correlate the logs. Which of the following choices BEST meets this need?
A. Nmap
B. Netcat
C. Wireshark
D. SIEM
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation are available at the end of this post.
SIEM
A security information and event management (SIEM) system provides a centralized solution for collecting, analyzing, and managing data from multiple sources. They combine the services of security event management (SEM) and security information management (SIM) solutions. A SEM provides real-time monitoring, analysis, and notification of security events, such as suspected security incidents. A SIM provides long-term storage of data, along with methods of analyzing the data looking for trends, or creating reports needed to verify compliance of laws or regulations.
SIEMs are very useful in large enterprises that have massive amounts of data and activity to monitor. Consider an organization with over 1,000 servers. When an incident occurs on just one of those servers, administrators need to know about it as quickly as possible. The SIEM provides continuous monitoring and provides real-time reporting. For example, in a large network operations center (NOC), the SIEM might display alerts on a large heads-up display. A benefit is that the monitoring and reporting is automated with scripts with the SIEM.
Vendors sell SIEMs as applications that can be installed on systems, and as dedicated hardware appliances. However, no matter how a vendor bundles it, it will typically have common capabilities. This starts with a database that can be easily searched and analyzed. The SIEM collects log data from devices throughout the network and stores these logs in the database.
SIEMs Capabilities
The following outline some additional capabilities shared by most SIEMs:
• Aggregation. Aggregation refers to combining several dissimilar items into a single item. A SIEM can collect data from multiple sources, such as firewalls, intrusion detection systems, proxy servers, and more. Each of these devices formats the logs differently. However, the SIEM can aggregate the data and store it in such a way that it is easy to analyze and search.
• Correlation engine. A correlation engine is a software component used to collect and analyze event log data from various systems within the network. It typically aggregates the data looking for common attributes. It then uses advanced analytic tools to detect patterns of potential security events and raises alerts. System administrators can then investigate the alert.
• Automated alerting. A SIEM typically comes with predefined alerts, which provide notifications of suspicious events. For example, if it detects a port scan on a server, it might send an email to an administrator group or display the alert on a heads-up display. SIEMs also include the ability to create new alerts.
• Automated triggers. Triggers cause an action in response to a predefined number of repeated events. As an example, imagine a trigger for failed logons is set at five. If an attacker repeatedly tries to log on to a server using Secure Shell (SSH), the server’s log will show the failed logon attempts. When the SIEM detects more than five failed SSH logons, it can change the environment and stop the attack. It might modify a firewall to block these SSH logon attempts or send a script to the server to temporarily disable SSH. A SIEM includes the ability to modify predefined triggers and create new ones.
• Time synchronization. All servers sending data to the SIEM should be synchronized with the same time. This becomes especially important when investigating an incident so that security investigators know when events occurred. Additionally, large organizations can have locations in different time zones. Each of these locations might have servers sending data to a single centralized SIEM. If the server logs use their local time, the SIEM needs to ensure that it compensates for the time offset. One method is to convert all times to Greenwich Mean Time (GMT), which is the time at the Royal Observatory in Greenwich, London.
• Event deduplication. Deduplication is the process of removing duplicate entries. As an example, imagine 10 users receive the same email and choose to save it. An email server using deduplication processing will keep only one copy of this email, but make it accessible to all 10 users. Imagine a NIDS collects data from a firewall and a SIEM collects data from the NIDS and the firewall. The SIEM will store only a single copy of any duplicate log entries, but also ensure that the entries are associated with both devices.
• Logs/WORM. A SIEM typically includes methods to prevent anyone from modifying log entries. This is sometimes referred to as write once read many (WORM). As logs are received, the SIEM will aggregate and correlate the log entries. After processing the logs, it can archive the source logs with write protection.
The location of the SIEM (and the location of its correlation engine) varies based on how the SIEM is used. However, it’s common to locate the SIEM within the private network, even if it is collecting some data from the demilitarized zone (DMZ). The internal network will provide the best protection for the log data. In very large organizations, aggregation processes and the correlation engine can consume a lot of processing power, so organizations sometimes off-load these processes to another server. The primary SIEM appliance can then focus on alerts and triggers.
Q. An organization has a large network with dozens of servers. Administrators are finding it difficult to review and analyze the logs from all the network devices. They are looking for a solution to aggregate and correlate the logs. Which of the following choices BEST meets this need?
A. Nmap
B. Netcat
C. Wireshark
D. SIEM
Answer is D. A security information and event management (SIEM) system provides a centralized solution for collecting, analyzing, and managing data from multiple sources and can aggregate and correlate logs.
None of the other choices aggregate and correlate logs.
Nmap is a network scanner that can discover and map devices on a network.
Netcat is a command-line tool that can be used to connect to servers.
Wireshark is a graphical-based protocol analyzer.
See Chapter 8 of the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide for more information on using security tools.