What is Steganography?
Steganography is the practice of hiding secret information in regular files. These files can be image files, audio, or video. It is in such a way that only the intended recipient knows of its existence. Unlike encryption, steganography conceals the fact that there is any hidden information at all.
The word "steganography" comes from the Greek words steganos, meaning "covered" or "concealed," and graphein, meaning "to write." Many people have used it throughout history for secret communication.
How Steganography Works
Steganography hides the message within a carrier file. The message could be in any form: text, image, or even audio. But the carrier file is usually a common file like an image or audio file that doesn't arouse suspicion. Here’s how it works:
- Embed the Message: A secret message is embedded in a larger, more innocent-looking file. For example, an image may have some pixel values changed to store information.
- Send the File: The modified file is then sent, and to any observer, it looks like a normal image or audio file. There is no obvious sign that it contains hidden information.
- Retrieve the Message: The recipient knows how to find the message. They can use a special tool or algorithm to extract the hidden information from the file.
Types of Steganography
Steganography has evolved significantly over the years, employing a range of sophisticated techniques. Here are some common methods used:
- Image steganography: Hides secret information in the least significant bits (LSB) of pixel data. It changes color values in a way that people cannot see.
- Audio steganography: Hides data by changing the frequencies, amplitude, or phase of sound waves. It uses the human ear's limited ability to notice small changes.
- Video steganography: It can hide data in the frames or motion vectors of a video. This method takes advantage of the large amount of data in video files.
- Text steganography: Involves changing the format of a text file. This can include altering spacing, font sizes, or character codes. These changes help hide information within the text.
Steganography And Cryptography
|
Feature |
Steganography |
Cryptography |
|---|---|---|
|
Goal |
To conceal the existence of secret data within a cover media. |
To turn a message into an unintelligible form, making it difficult to decipher without a key. |
|
Method |
Modifies the cover media in a way that hides the message, making it appear as part of the media itself. |
Encrypts the message using a mathematical algorithm and a key, transforming it into ciphertext. |
|
Security |
Relies on the obscurity of the hiding method and the difficulty of detecting the hidden message. |
Depends on the strength of the encryption algorithm and the secrecy of the key. |
|
Detection |
Can be difficult to detect if done well but may leave subtle artifacts or distortions in the cover media. |
Easier to detect, as the ciphertext will look random and unrelated to the original message. |
|
Example |
Hiding a message within the least significant bits of an image or audio file. |
Using a Caesar cipher to shift each letter of the alphabet by a certain number of positions. |
|
Use Cases |
Protecting sensitive information, covert communication, digital watermarking. |
Protecting data in transit, securing online transactions, protecting stored data. |
|
Real-World Analogy |
Hiding a letter inside a hollowed-out book. |
Locking a letter in a box with a padlock. |
|
Main Vulnerability |
If the existence of hidden data is detected, the message can be easily extracted. |
If the encryption key is compromised, the entire message can be decrypted. |
How Steganography is Used to Deliver Attacks
- Hiding Malware: Malicious code can be embedded within seemingly innocent images or audio files. When these files are downloaded and opened, the hidden malware is executed. Malware can be concealed within text documents, spreadsheets, or presentations.
- Command and Control (C2) Communication: Steganography can be used to establish covert communication channels between a compromised system and a malicious server. This allows attackers to maintain control over infected systems without being detected. Sensitive data can be exfiltrated from a compromised network by embedding it within seemingly legitimate files or traffic.
- Social Engineering: Malicious attachments can be hidden within seemingly legitimate files, tricking victims into opening them and executing the hidden malware. Attackers may compromise websites frequented by a specific target group and embed malware within the content.
- Botnet Communication: Botnet operators can use steganography to communicate with compromised devices and coordinate DDoS attacks. Botnets can be used to steal sensitive data, which can then be exfiltrated using steganography.
- Evasion Techniques: Steganography can be used to hide malware from detection by antivirus software. By embedding malicious traffic within legitimate traffic, attackers can evade detection by NIDS.
Examples of steganography used in cyber attacks
Stegano Exploit Kit (2016)
The Stegano exploit kit used banner ads on popular websites to secretly deliver malicious code. Hackers hid JavaScript code within the pixels of these ads. When users visited pages with these ads, their computers would unknowingly download harmful code. This code could lead to more malware infections.
This attack was successful because the ads reached many people. It showed how attackers can use online advertising to spread hidden malware. The code was embedded in images, making it difficult for regular antivirus software to detect.
Operation ShadowHammer (2019)
In this attack, cybercriminals hid malicious code within legitimate ASUS software updates. They used steganography to embed this harmful code. When people installed the updates, they were also installing malware.
Because the updates looked real and had digital signatures, many antivirus programs didn't detect them. The attack affected over a million devices. This shows how even trusted software can be used to spread malware.
Poison Ivy and Malvertising Campaigns (2013)
Malvertising campaigns have been known to use steganography to evade detection by embedding exploit code in banner ads. Poison Ivy, a remote access Trojan (RAT), was deployed through ads containing steganographic code embedded in images. When users clicked on these ads, they inadvertently executed code that installed the RAT.
This allows attackers to access their systems remotely. The malicious payload was hidden within the images, bypassing traditional security tools that checked file integrity without scrutinizing embedded data.
Steganalysis: Detecting Steganography Made Easy
Steganalysis and steganography detection employ various methods to uncover hidden information within digital files.
Visual Inspection
For image-based steganography, a simple method is to visually compare the original file with the stego-object. This might reveal subtle distortions or pixel irregularities. Modern techniques modify the least significant bits (LSBs) of pixel values, making changes imperceptible to the human eye.
File Structure Analysis
Compare the structure of a file to a known original format. Hidden data often alters the file size or structure in subtle ways. Tools can analyze the header, metadata, and other file characteristics to detect anomalies. A normal JPEG file has a predictable structure.
Any irregularities in the size, unused space, or additional metadata could indicate steganography. Skilled steganographers may use compression or data encoding to avoid detectable changes in file structure.
Statistical Analysis
This method looks for statistical irregularities in the content of a file. For example, in images, it detects variations in pixel color frequency or distribution. In audio files, it checks for unusual patterns in sound waves.
Some statistical methods include frequency analysis, chi-squared tests, and histogram analysis. A natural image has a predictable distribution of colors and noise. Altering the least significant bits (LSBs) to embed data can introduce detectable statistical inconsistencies.
Noise and Distortion Detection
Hidden data in an image often introduces noise or distortion. Tools can compare the noise levels in different parts of the image and identify discrepancies. The introduction of hidden data can increase the amount of noise, especially in smooth areas of an image.
Steganalysis tools detect abnormal noise levels. Advanced steganography techniques may use noise-reducing algorithms or sophisticated encoding that make noise detection difficult.
Conclusion
Steganography is a covert communication technique that hides secret messages within ordinary files. Unlike encryption, which disguises data, steganography conceals information in plain sight.
Cybercriminals have exploited it in attacks. Detecting steganography requires advanced techniques. To mitigate the threat, organizations must implement robust security practices and employ advanced detection tools.
FAQS
What is steganography?
Steganography definition is a covert communication technique that involves embedding hidden information within ordinary media files, such as images, audio, or text. Unlike encryption, steganography conceals information in plain sight, making it difficult to detect.
How does steganography differ from encryption?
Encryption transforms data into a seemingly random code, making it unreadable to anyone without the correct decryption key. Steganography, on the other hand, hides information within existing data, making it appear as part of the original content.
How can steganography be detected and prevented?
Detecting steganography requires advanced techniques such as statistical analysis, visual inspection, and machine learning. To stop steganographic attacks, organizations can take several steps.
They can use data loss prevention measures and monitor network traffic. Educating employees is also important. Regular security audits help find weaknesses. Finally, using special detection tools can improve security.
