Indicators of Malware Attacks (Domain 2)
In this episode, we are focusing on indicators of malware attacks—specifically, how to recognize signs of infection and understand the different types of malicious software that may be involved. Malware is constantly evolving, but it often leaves clues behind. Knowing what to look for can make the difference between early detection and a full-scale breach. We’ll cover ransomware, traditional malware types like trojans and worms, surveillance tools like spyware and keyloggers, and hidden threats like logic bombs and rootkits.
Let’s begin with ransomware. Ransomware is a type of malware that encrypts a victim’s files and demands payment—usually in cryptocurrency—to restore access. The first and most obvious indicator of ransomware is a ransom note. This message may appear as a popup window, a changed desktop background, or a file named "readme" or "decrypt" placed in each affected folder.
Another common sign is a sudden change in file extensions. Files that previously opened normally now have extensions like “dot locky,” “dot cry,” or “dot encrypted” and cannot be opened with standard software. The encryption process may also cause system slowdowns, especially on machines with large volumes of files.
High-profile ransomware incidents have targeted hospitals, city governments, and major corporations. In one case, an entire municipal network was locked down, and attackers demanded hundreds of thousands of dollars. Services were halted, public records became inaccessible, and the recovery process took months.
To detect and respond to ransomware, organizations should monitor for changes in file extensions, large volumes of file writes in a short time, and processes that rapidly access multiple files. Backups should be kept offline or in immutable storage, and endpoint protection should include behavior-based detection—not just signature scanning.
Now let’s turn to classic malware types like trojans, worms, and viruses. A trojan is a piece of malware that disguises itself as legitimate software. Once executed, it may open backdoors, steal data, or install additional malicious tools. Signs of a trojan include sudden system slowdowns, unexpected network activity, or software behaving differently than expected.
Worms are self-replicating programs that spread from system to system without user interaction. They often consume bandwidth and system resources as they replicate. You might notice increased CPU or memory usage, duplicate files, or multiple instances of the same process running. A virus is similar but typically relies on a user action—like opening a file or launching a program—to begin spreading. Once active, viruses may corrupt files, disable system functions, or degrade performance.
To prevent these infections, users should avoid downloading untrusted files or clicking unknown links. Systems should have updated antivirus and intrusion detection tools in place. Segmentation and regular patching help stop worms from spreading laterally across networks.
Now let’s explore spyware, keyloggers, and bloatware. Spyware is designed to collect information without the user’s knowledge. It may track web activity, log keystrokes, capture screenshots, or send data back to a remote server. Keyloggers are a type of spyware that specifically record every keystroke—making them especially dangerous for capturing passwords and credit card numbers.
Bloatware, on the other hand, refers to pre-installed or unnecessary software that clutters a system and reduces performance. While not always malicious, bloatware may include adware, trackers, or promotional tools that degrade user privacy and open the door for additional threats.
Signs of spyware and keyloggers include unexplained lag during typing, browsers redirecting to unfamiliar sites, excessive popups, and unusually high outbound network traffic. A user may also notice unknown programs listed in the task manager or unfamiliar services running in the background.
Privacy-focused monitoring tools, endpoint detection systems, and regular scans can help uncover spyware. Removing bloatware may require system reinstallation or specialized cleaning tools. Policies should restrict unnecessary software installation and limit administrative privileges to reduce the chance of infection.
Finally, let’s examine logic bombs and rootkits. A logic bomb is code that sits dormant until triggered by a specific event—such as a date, system condition, or user action. Once triggered, it may delete files, crash systems, or launch other forms of malware. Logic bombs are hard to detect until they activate. Symptoms appear suddenly and may resemble a software glitch or hardware failure.
Rootkits are among the most dangerous types of malware. They are designed to hide their presence and give attackers administrative control over the system. Rootkits operate at a low level, often below the operating system, and can mask processes, files, or registry entries to avoid detection.
Detecting rootkits is difficult. Normal antivirus tools may not see them at all. Signs include disabled security software, persistent malware that reinstalls after deletion, and system logs that don’t match actual events. Specialized rootkit detection tools and forensic analysis are often needed to find and remove these threats.
Preventing rootkit infections starts with securing the initial system image, enforcing strong access controls, and using hardware-based verification like secure boot and trusted platform modules. Systems suspected of harboring a rootkit may need to be wiped and rebuilt from known-good sources.
As you prepare for the Security Plus exam, understand the different types of malware and the signs they leave behind. You may be asked to identify ransomware based on encrypted files, or a worm based on spreading behavior. You might also need to recognize the symptoms of spyware or explain how rootkits evade detection. Be ready to choose appropriate response strategies based on the type of malware and the depth of its integration with the system.
