1. Program Security

Program security refers to the practice of designing, developing, and maintaining software applications in a way that prevents unauthorized access, data breaches, and malicious exploitation. Security vulnerabilities in programs can lead to serious consequences, such as data theft, system compromise, and service disruptions. Ensuring program security is crucial in an era where cyber threats are becoming increasingly sophisticated.

Software vulnerabilities can be exploited by attackers to manipulate applications, steal sensitive information, or cause system failures. Therefore, security must be an integral part of the software development lifecycle (SDLC) to minimize risks.

Key Security Properties

A secure program should adhere to three fundamental properties:

1. Confidentiality – Ensuring that sensitive information is only accessible to authorized users. Attackers should not be able to gain access to confidential data stored in or processed by a program.
2. Integrity – Ensuring that data and system functions remain unaltered by unauthorized entities. Programs should continue to function correctly even in the presence of an attacker.
3. Availability – Ensuring that authorized users can access the system and its resources without disruptions caused by malicious attacks.

Incorporating these properties into software development helps build robust applications that are resistant to attacks and data breaches.

2. Common Security Vulnerabilities in Programs

Various vulnerabilities can exist in programs due to coding errors, inadequate validation mechanisms, or misconfigurations. Below are some of the most common security vulnerabilities that attackers exploit:

1. Buffer Overflow

Buffer overflow occurs when a program writes more data to a buffer (a temporary storage location in memory) than it was designed to hold. This overflow can overwrite adjacent memory locations, leading to unexpected behavior, crashes, or even code execution by an attacker.

Example of Buffer Overflow Attack:

• The Morris Worm exploited a buffer overflow in the fingerd service, infecting 10% of the early Internet’s machines.
• SQL Slammer spread rapidly by exploiting a buffer overflow in Microsoft SQL Server.

2. SQL Injection Attack

SQL Injection (SQLi) occurs when an attacker manipulates SQL queries by injecting malicious input into a web application's database query. This can allow unauthorized access to data, database modification, or even deletion of critical records.

Example of SQL Injection Attack:

• Attackers enter " OR 1=1" in login forms to bypass authentication.
• Malicious input such as DROP TABLE Users; can be used to delete entire databases.

3. Incomplete Mediation

Incomplete mediation refers to cases where user input is not properly validated before being processed. Attackers can exploit such vulnerabilities by submitting unexpected input, bypassing restrictions, or manipulating hidden form fields in web applications.

Example of Incomplete Mediation Attack:

• A website might restrict date inputs in a calendar but still accept out-of-range values through direct URL manipulation, potentially breaking the application.

4. Time-of-Check to Time-of-Use (TOCTTOU) Errors

TOCTTOU vulnerabilities arise when a program checks a condition before performing an operation, but the system state changes between the check and execution. This is particularly dangerous in multi-threaded or multi-user environments.

Example of TOCTTOU Attack:

• A file access permission check occurs, but before the file is opened, an attacker swaps it with a different file, bypassing security restrictions.

5. Format String Vulnerabilities

Format string vulnerabilities occur when a program improperly handles user-supplied input in functions like printf(), sprintf(), or fprintf(). If an attacker can control the format string, they can read arbitrary memory contents or even write to memory locations, leading to serious security breaches such as information leakage, memory corruption, or code execution.

Example of Format String Attack:

• Attackers use %x%x%x to leak stack memory contents, which may reveal sensitive data like passwords or memory addresses.
• Using %n, an attacker can overwrite specific memory locations, potentially altering control flow or escalating privileges.

Now, let’s have a detailed look at each of the above vulnerabilities.

3. Buffer Overflow Attacks

A buffer overflow occurs when a program writes more data to a buffer—a contiguous block of memory—than it can hold. This excess data can overwrite adjacent memory, leading to unpredictable behavior, crashes, or the execution of malicious code. Buffer overflows typically result from inadequate bounds checking during operations like copying or concatenating strings.