Malware refers to any software developed with malicious intent to harm computer systems, networks, mobile devices, or users; gain unauthorized access; or steal confidential data. Derived from the term “malicious software,” it represents one of the most common digital threats to modern information systems. Malware poses risks to both individual privacy and the integrity of organizational infrastructures.

The history of malware dates back several decades. The first known example, the “Creeper” program, was developed in the United States in 1971 and spread through ARPANET, displaying the message “I’m the Creeper, catch me if you can!” on affected systems. Later, in 1986, the “Brain” virus developed in Pakistan became the first PC virus to spread globally. In 1988, the “Morris Worm” written by Robert Morris propagated across the internet, crashing thousands of systems and revealing the potential scale of the malware threat. The term "malware" began to appear more frequently in academic literature starting in the 1990s.

Malware can spread through various methods. Common methods include email attachments, fake websites, USB drives, and social engineering attacks. With the rise of mobile device usage, malware also spreads through mobile applications. For instance, a fake APK version of the mobile game Pokémon GO contained a malware known as DroidJack, which enabled remote access to the victim’s SMS messages, contacts, camera, and microphone for espionage purposes. Such threats not only endanger personal privacy but also create significant vulnerabilities when infiltrating corporate networks.

Precautions against malware fall into two categories: technical and behavioral. The regular use of antivirus software and firewalls constitutes a primary technical defense. Moreover, keeping software updated, avoiding unlicensed or unverified programs, and downloading mobile applications only from official stores are crucial user practices. User awareness plays a critical role, particularly in recognizing phishing emails and fake links. System maintenance software also provides additional protection against malware by preserving disk integrity, cleaning the registry, and monitoring suspicious activity.

^{Image Representing Malware (AA)}

Main Types

Malware is classified in various ways according to the nature of its activities and its impact on the system. These types serve different purposes, such as stealing data, rendering systems unusable, gaining unauthorized access, or deceiving the user:

1. Computer Viruses: These programs can replicate by attaching themselves to other files or software. When executed, they may damage or alter data on the target system. They commonly spread through email attachments, downloaded programs, and removable media. File viruses target executable files such as .exe or .bat, while macro viruses can infect Microsoft Office documents. Polymorphic and stealth viruses encrypt their code to avoid detection and evade analysis.
2. Trojans: Disguised as legitimate software, Trojans perform malicious actions without the ability to self-replicate. They can create a backdoor that enables unauthorized access to the user’s system. Some Trojans capture keystrokes to steal credentials, while others delete system files or alter configurations, rendering the device inoperable.
3. Worms: Spreading through network protocols or operating system vulnerabilities, worms replicate without user interaction. They consume system resources, degrade performance, and can lead to widespread service disruptions. Worms are especially dangerous in enterprise networks due to their rapid propagation.
4. Spyware: These programs covertly collect personal data such as browsing history, location, passwords, and identity information, transmitting it to remote servers. Spyware often installs alongside free software or masquerades as adware.
5. Backdoors: Designed to provide unauthorized access or persistent control over a system, backdoors allow attackers to connect to the system at will. They often serve as entry points for other types of malware.
6. Adware: These programs display advertisements on the user’s screen without consent and may impair system performance. Some adware collects user behavior data to deliver targeted ads, generating revenue for the attacker.
7. Ransomware: This type of malware encrypts the victim’s data and demands payment for its release. It typically uses cryptographic algorithms to block access to files. Variants like “Cryptolocker” threaten to delete data if the ransom is not paid, exerting pressure on the user.
8. Keyloggers: These tools record keystrokes to capture sensitive information such as usernames, passwords, and credit card numbers. Keyloggers are commonly used in financial fraud, particularly targeting online banking activities.

Methods of Propagation

Malware typically spreads through user interaction or by exploiting system vulnerabilities. The most common methods of propagation include:

• Email Attachments: Malicious links or infected file attachments sent via phishing emails.
• Fake Software: Malware distributed through counterfeit versions of legitimate software or games, such as offering a paid application as a “free APK” file.
• Web Browser Vulnerabilities: Exploits and malicious advertisements can take advantage of security flaws in browsers to infect systems.
• USB Drives and Removable Media: Malware can spread through portable devices using auto-run features.
• Mobile Applications: Particularly on the Android operating system, applications downloaded from outside the official app store may contain malicious code. In this method, malware embedded in a popular app can reach a wide audience.

Reflections in the Mobile Environment

As the hardware capabilities and multifunctionality of mobile devices have increased, they have become targets for attackers. Activities such as mobile banking, email communication, and personal data storage conducted via smartphones have drawn the attention of malware developers to these devices. Malware on mobile platforms is typically embedded within applications. For instance, a malicious program inserted into a counterfeit version of a popular mobile game may gain extensive permissions once installed on the device, including sending SMS messages, accessing the camera, retrieving call logs, tracking location, and transferring files. Such malware grants attackers full control over the device, posing a serious threat to user security.

Analysis and Detection Processes

The study of malware involves analyses conducted to identify its type and determine its effects. These analyses are divided into two main categories:

• Dynamic Analysis: Involves running the malware in a virtual environment to observe its behavior. Activities such as network connections, file creation or deletion, and registry modifications are monitored to detect the software’s impact.
• Static Analysis: Involves examining the source code or binary content of the software without executing it. By analyzing file signatures, character strings, file headers, and encryption structures, detailed information about the malware can be obtained.

These analyses are crucial for both enabling security professionals to understand threats to the system and ensuring the traceability of malware in digital forensic investigations.

Countermeasures

There are both technical and behavioral precautions that can be taken against malware. Key protection measures include:

• Keeping antivirus and antimalware software up to date
• Regularly updating operating systems and applications
• Avoiding software downloads from unknown sources
• Implementing strong password policies
• Limiting administrative privileges to necessary users only
• Preventing uncontrolled use of USB devices
• Establishing file backup systems
• Disabling installation of applications from unknown sources on mobile devices

Users should also carefully review the permissions requested by mobile applications. For example, in suspicious cases such as a calculator app requesting SMS reading access, the installation should be avoided.

Legal Dimension

In Türkiye, the fight against malware is conducted through both technical and legal means. Within the scope of Law No. 5651 on the “Regulation of Publications on the Internet,” the obligations of content providers, hosting providers, and access providers are defined. Additionally, Articles 243 (unauthorized access to information systems), 244 (interference with and obstruction of data), and 245 (unlawful use of data) of the Turkish Penal Code contain provisions for offenses committed via malware. Accordingly, individuals who develop, distribute, or use malware may face criminal sanctions.

In the United States, the primary legislation on this issue is the Computer Fraud and Abuse Act (CFAA), which classifies acts such as unauthorized access and data theft as federal crimes. The European Union, under the General Data Protection Regulation (GDPR), considers the unlawful acquisition of personal data a data security breach and imposes severe administrative penalties on responsible individuals or organizations.

Malware represents one of the most dynamic and constantly evolving threats in the field of digital security. It poses serious risks to both individual users and corporate networks. As technology advances, the variety and complexity of malware increase, making it necessary to continuously update security measures. An effective defense requires high user awareness, up-to-date security software, and adherence to basic digital hygiene practices.