CompTIA CS0-002 - CompTIA CySA+ Certification Exam (CS0-002)

The best practice for establishing a digital certificate for a new application is to ensure the certificate is requested from a trusted CA. A CA stands for Certificate Authority, and it is an entity that issues and verifies digital certificates, which are electronic documents that contain a public key and a digital signature that prove the identity and authenticity of an application, a website, or a person. Requesting a certificate from a trusted CA can help ensure that the certificate is valid, secure, and recognized by other parties.

Requiring support teams to develop a corrective control that ensures security failures are addressed once they are identified is the best step to prevent future issues from being remediated. Corrective controls are actions or mechanisms that are implemented after a security incident or failure has occurred to fix or restore the normal state of the system or network. Corrective controls can include patching, updating, repairing, restoring, or reconfiguring systems or components that were affected by the incident or failure .

Based on the output of the “netstat -an” command, it seems that the web server is listening on port 80 for HTTP traffic and port 443 for HTTPS traffic. The anomalous traffic from 9.9.9.9 is accessing the web server on port 443, which means it is using a secure connection.

The best method to accomplish the task of restricting improper traffic from 9.9.9.9 is D. Adjusting the firewall. A firewall is a device or software that controls the flow of network traffic based on predefined rules. By adjusting the firewall rules, you can block or allow specific IP addresses, ports, protocols, or domains from accessing your web server.

The correct answer is B. The analyst should block requests to no-thanks.invalid. The log snippet shows a DNS query from host 192.168.1.67 to the public resolver 8.8.8.8 for the domain name no-thanks.invalid, which is resolved to the IP address 102.100.20.20. This is a possible indicator of compromise (IOC), as no-thanks.invalid is a known malicious domain that is used by attackers to exfiltrate data or execute commands on compromised hosts1. The analyst should block requests to this domain to prevent further communication with the attacker’s server and investigate the host 192.168.1.67 for signs of infection.

A. The analyst should disable DNS recursion is not correct. DNS recursion is a process where a DNS server queries other DNS servers on behalf of a client until it finds the authoritative answer for a domain name2. Disabling DNS recursion would prevent the DNS server from resolving any domain names that are not in its cache or zone files, which would affect the normal functionality of the network and the internet access of the clients.

C. The analyst should disconnect host 192.168.1.67 is not correct. Disconnecting host 192.168.1.67 would stop the communication with the malicious domain, but it would also disrupt the legitimate activities of the host and its user. Moreover, disconnecting the host would not remove the malware or root cause of the compromise, and it would not prevent the host from reconnecting to the malicious domain once it is online again.

D. The analyst should sinkhole 102.100.20.20 is not correct. Sinkholing is a technique that redirects malicious or unwanted traffic to a controlled destination, such as a fake or isolated server3. Sinkholing 102.100.20.20 would prevent the communication with the malicious domain, but it would also require access and control over the public resolver 8.8.8.8, which is not owned or managed by the analyst or the company.

E. The analyst should disallow queries to the 8.8.8.8 resolver is not correct. Disallowing queries to the 8.8.8.8 resolver would prevent the communication with the malicious domain, but it would also affect the resolution of other legitimate domain names that are not in the local DNS server’s cache or zone files.

1: DNS Tunneling: how DNS can be (ab)used by malicious actors 2: What Is DNS Recursion? 3: What Is a Sinkhole Attack?

A cipher suite is a set of algorithms that defines how the encryption, authentication, and integrity of data are performed during a secure communication session. Some cipher suites are considered vulnerable or weak because they use outdated or insecure algorithms that can be easily broken or compromised by attackers. The vulnerability scan results show that the web server accepts several vulnerable cipher suites, such as RC4, MD5, or DES. The best action for the analyst to recommend to developers is to change the web server so it no longer accepts the vulnerable cipher suites and only accepts the secure ones. Changing the web server so it only accepts TLSv1.2, only accepts cipher suites using AES and SHA, or offloading SSL/TLS to a WAF and load balancer are other possible actions, but they are not as specific or effective as changing the web server so it no longer accepts the vulnerable cipher suites. Reference: https://www.acunetix.com/blog/articles/tls-ssl-cipher-hardening/

A retinal scan is a biometric authentication method that uses the unique pattern of blood vessels in the retina to verify a person’s identity. It is considered a strong and reliable authentication method that would enhance the datacenter’s security. A physical key, a passphrase, or a fingerprint are other authentication methods, but they are not as secure or reliable as a retinal scan. Reference: https://www.techopedia.com/definition/2586/retinal-scan

A cloud access security broker (CASB) is a security solution that monitors and controls the use of cloud-based services and applications. A CASB can provide data loss prevention (DLP) capabilities for sensitive data that is being stored in the cloud, such as encryption, masking, tokenization, or redaction. A CASB can also enforce policies and compliance requirements for cloud usage, such as authentication, authorization, auditing, and reporting. The other options are not appropriate solutions for controlling sensitive data in the cloud. References: CompTIA Cybersecurity Analyst (CySA+) Certification Exam Objectives (CS0-002), page 14; https://docs.microsoft.com/en-us/cloud-app-security/what-is-cloud-app-security

The analyst decided to include a custom lookup for these files on the endpoint’s log-in script as a mechanism to improve existing detection capabilities, by checking if any of these files are present on the endpoints during log-in. This can help identify any compromised endpoints that may have been infected by the zero-day vulnerability, and alert the analyst for further investigation or response.

An eFuse, or electronic fuse, is a microscopic fuse put into a computer chip that can be blown by applying a high voltage or current. Once blown, an eFuse cannot be reset or repaired, and its state can be read by software or hardware2 An eFuse can be used by a hardware manufacturer to prevent firmware downgrades on a system-on-chip (SoC) that will be used by mobile devices. An eFuse can store information such as the firmware version, security level, or device configuration on the chip. When a newer firmware is installed, an eFuse can be blown to indicate the update and prevent reverting to an older firmware. This can help protect the device from security vulnerabilities, compatibility issues, or unauthorized modifications.

The correct answer is D. Use a VPN to access the company’s data in the home office and keep the current solution for the business applications. A virtual private network (VPN) is a technology that creates a secure and encrypted connection over a public network, such as the internet. A VPN can allow users to access resources on a remote network, such as a server, as if they were on the same local network. A VPN can provide shared access from the remote office to the company’s data in the home office, while maintaining security and privacy1.