Linux Commands for Testers

In today’s security system development environment, several essential tools and commands test engineers frequently use to monitor and defend against potential threats. These commands help in ensuring system integrity, tracking security breaches, and diagnosing network issues. Below are some of the most widely used UNIX commands:

nslookup

nslookup is a command-line tool used to query DNS records associated with a domain name or IP address. It helps resolve domain names to IP addresses and can be used for troubleshooting DNS-related issues.

getmac

The getmac command retrieves the MAC address of the network interfaces on the system, along with the network protocols associated with each address. This information can be useful for identifying network devices and troubleshooting network issues.

hping

hping is an open-source network tool that generates custom TCP/IP packets and analyzes responses. It’s used for testing firewalls, performing advanced port scanning, and auditing the TCP/IP stack. hping can also be used to send massive volumes of TCP traffic to a target while spoofing the source IP.

ping

The ping command is used to check the connectivity between the local machine and a remote server by sending packets to the server’s IP address or hostname. It measures the round-trip time (RTT), indicating how long it takes for a packet to travel from the source to the destination and back. It typically uses the ICMP protocol to request and receive replies.

curl

The curl command is used to transfer data over multiple protocols, including HTTP, FTP, and SMTP. It’s often used for testing web applications, downloading files, or sending data to remote servers.

netstat

The netstat command shows the status of all network connections, listening ports, and associated processes. It helps security engineers identify unauthorized services or suspicious connections established from remote hosts.

route

The route command allows users to view or modify the host’s local routing table. By default, all traffic is routed through the default gateway, but suspicious entries in the routing table might indicate potential security threats or misconfigurations.

wireshark

Similar to tcpdump, wireshark is a graphical network protocol analyzer used to capture and analyze network packets. It provides a more user-friendly interface, making it easier to interpret and inspect traffic in depth.

lsof

lsof (List Open Files) is a command that shows all open files on the system, along with the processes that opened them. It’s particularly useful for security investigations, as it can help identify suspicious files or processes that may be running on the system.

scanless

scanless is a tool that automates the process of scanning a host’s open ports and services. It helps security professionals identify vulnerabilities and weaknesses in the system by providing detailed scans of the services running on a network.

nmap

nmap is a powerful network scanning tool that can identify open ports, services, and vulnerabilities on a network. It uses various scanning techniques to probe a target system and provide comprehensive information about its network services and exposed vulnerabilities.

memdump

The memdump command is used to display a hexadecimal dump of memory, beginning at a specified address. It is used for debugging, forensic investigations, and security auditing.

tcpreplay

The tcpreplay command replays network traffic that has previously been captured and saved in .pcap files. It is useful for network testing, penetration testing, and simulating network conditions.

free

The free command displays the amount of free and used memory on the system. It’s an essential tool for monitoring system resources and identifying potential issues related to memory usage.

dig

dig (Domain Information Groper) is a tool used to query DNS records. Unlike nslookup, dig can query multiple DNS servers at once and provide more detailed information, making it an excellent tool for troubleshooting DNS issues and performing DNS lookups.

arp

The arp command displays the Address Resolution Protocol (ARP) cache on a local machine. The ARP cache contains the MAC addresses of network interfaces that have recently communicated with the local host, mapped to their corresponding IP addresses. This command can also be useful in detecting spoofing attacks on the network.

openssl

openssl is a toolkit for working with cryptographic protocols and tools. It is used to generate SSL/TLS certificates, private keys, create certificate signing requests (CSRs), and perform various cryptographic operations essential for securing communications.

mtr

mtr (on Linux) is an advanced network diagnostic tool that combines the functionalities of ping and traceroute. They help assess network latency and packet loss at intermediate hops between a source and a destination, offering detailed insights into the network path.

isattr

isattr displays the attributes of a specified device or file. This command helps security engineers check the attributes set on a particular file or device, which may be useful for auditing and security monitoring.

tcpdump

tcpdump is a packet analyzer that allows engineers to capture and analyze network traffic in real-time. It’s especially useful for security professionals looking to troubleshoot network issues or analyze malicious traffic patterns. The captured data can be saved in .pcap files for further analysis.

dd

The dd command is used to copy raw data between disks or files. It is often used for creating disk images or backups, as well as for cloning and duplicating data on storage devices.

netcat

Known as the “Swiss Army knife” of networking, netcat is a versatile tool used for reading and writing data between hosts over the network. It can be used for debugging, network exploration, and setting up reverse shells, making it a valuable asset for security engineers.