What is Alternate Data Stream And Why It is Important
If you are an IT professional, software developer, or other party that needs access to comprehensive data, you need to know what an alternate data stream is. Alternate Data Streams (ADS) within a file system, including within the NTFS framework on Windows operating systems, play a significant role in data security.
Table of Contents
In this article, we will explore ADS, its technical aspects, and its legitimate uses. We will also explore some of the risks associated with security when ADS is present, including how to detect and manage it once found.
Understanding Alternate Data Streams
What is an ADS file? An alternate data stream enables a single file to contain more than one stream of data within it. Each of those streams may store different types of information. Some of that information is not easily found with a traditional file view, and that’s where the problem lies if you allow it to pass through your security methods.
There are various reasons why ADS can be used. For example, it can attach metadata or store additional information you want to pass along without altering the primary file content. In all cases, it impacts how data is managed and secured within the NTFS.
Why are ADS used? There are numerous potential reasons for this. To understand it, consider file systems themselves. These systems are critical to the way operating systems manage and store data. NTFS (New Technology File System) is a high-performance file system created by Microsoft. It’s very heavily used because it can handle large amounts of data with various file sizes and offers security features, including file encryption.
ADS is one of the unique features that NTFS offers. It is not considered a bad thing, as it can be very useful in communicating data that needs to be sent, but it does so without altering the initial or primary data. Multiple streams of data like this are not uncommon. Some of the most common legitimate uses for ADS include:
- Metadata storage: This is a very common reason for using ADS. It allows for the storage of the author’s information, descriptive text, or titles but does not change the main file content.
- System processes: Windows will use ADS itself to maintain system-level information. This might include indexing attributes or, in some cases, security descriptors. This ultimately helps improve the system’s operational efficiency.
- Functionality improvement: In some situations, configuration data, thumbnails, or other data is shared to supplement or improve the way the file is used.
These are some of the most common, but not all, ways that this data may be applicable. But how does it all work?
How ADS Works in NFTS
Before diving into others, let’s take a look at the Windows alternate data stream, ADS, in NTFS. In NTFS, a primary stream is the main content of the file. The alternate streams provide access to additional information. These other streams are not visible within standard file listings. Instead, to capture this information and find it, a specific tool or API is necessary.
The syntax to access the ADS will include appending a colon and the stream name of the file path. In other words, you need to know what you’re looking for to find it. Here’s an example:
File.txt:stream
ADS In Other File Systems Exist
Most of the time, those using Windows will use NTFS. However, there are other file systems and storage methods that have somewhat the same functional elements that allow for multiple data streams to be shared. Most of the tools you have will offer something. Some examples that may apply include:
Apple File System: APFS is a newer option for macOS and iOS. It supports extended attributes, which is much like Ads. This allows metadata to be attached to files, for example.
Hierarchical File System Plus: HFS+ is an older version of macOS that includes forks, which are somewhat like ADS. It allows metadata and other attributes to be stored with the main data fork.
Extended File Systems: This includes Ext2, Ext3, and Ext4, all of which are used on the Linux operating system. They support the extended attributes of (xattr), which allows for metadata storage.
If you’re using another operating system, you need to look specifically for the multiple-stream solutions available. These are the most commonly used.
Are Alternate Data Streams Bad?
What are Alternate Data Streams from a less-than-desirable standpoint? Though they are easily used for various applications to send valuable data, there are some ways they can be used to wreak havoc. Unfortunately, it is common for ADS to be misused to hide data, viruses, or malware. Because you do not know they are there, they can easily be put into your system. Then, those working against you can exploit the feature using the code to achieve their goal.
There are various ways this can happen. For example, the use of a Trojan horse program could occur. In this situation, the ADS is used to hide malware, and it will get right past your traditional antivirus scan. Other threats include persistent mechanisms and data exfiltration.
We never encourage you to engage in any type of activity that is illegal. In fact, when you learn more about how Scraping Robot works, you’ll see that we strongly encourage you to only use these tools for legal and allowable reasons. We have also created tutorials to help you overcome some of the challenges faced with web scraping, such as how to avoid honeypot traps. You can use our tools to help you overcome the most common anti-scraping techniques, too.
Still, these are all legal strategies. We do not encourage you to overstep the terms of any website.
How to Detect and Manage ADS
As a software developer or other data pro, you already know the importance of protecting your system. How can you protect yourself from something you don’t know is there, then?
There are various ways you can do so, and in short, you should use more than one. An alternate data stream is not something you want to let get by you. For that reason, we encourage you to do the following:
- Scan for ADS using a dedicated tool and script. Consider the Sysinternals Streams tool, a free application, or PowerShell scripts.
- Put in place policies that help prevent risks. For example, within your company, you should establish that ADS should not be used for any non-essential purposes. This type of policy should specifically outline what legitimate functions of ADS are within your scope of operations.
- Most people don’t know much about the implications of an Alternate Data Stream. Educate your team on the potential risks associated with it.
If you are looking for solutions for various tasks, such as how to use “convert an ADS file,” it’s a good idea to start by running a scan on your system to detect the presence of ADS.
Alternate Data Streams and Web Scraping
The use of an alternative data stream is becoming quite common when we consider how companies are using web scraping to achieve their objectives. If you think about the future of web scraping, you’ll likely see how this applies.
For example, alternate data may come from various organizations, including news feeds, financial statements, or surveys from your customers. Using alternative data streams to gain valuable insight into consumer behavior and competitor analysis enables better insight into what other companies are doing and why.
We encourage you to learn as much as possible about alternate data streams and why they should matter to your web scraping and file sharing. Data security has never been more important, and there is an increasing risk of malicious behavior from bad actors.
One of the ways you can minimize the risks you face when it comes to web scraping is to use a proxy service. A proxy is a type of intermediary that sits between your device making the request and the website receiving that request. Proxies allow you to gain an additional layer of protection and potentially minimize the risk of unknown infections happening. For example, you can use a residential proxy to import layers of protection that reduce the risk of sensitive information slipping by you. Learn how to set up a proxy. Then, learn how to use a web scraping proxy for protection.
Let Scraping Robot Go to Work for You
Scraping Robot’s web scraping API is always available. It helps you capture just the information you need and want for valuable decision-making. Contact Scraping Robot now with any questions you may have, or get started using our tools now.cv
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