What is a Replay attack? On MiniTool Website, many kinds of attacks have been introduced, such as DNS attack, Evil Twin attack, DDoS attack, and DoS attack. In this article, you will learn a new type – Replay attack and the post will try best to clarify the definition in an easy way.

What Is a Replay Attack?

In this computing world, data caries too much privacy beyond your imagination. You exchange information, upload your ID card, share your daily life, shop on the Internet. The whole Internet circle can be regarded as a giant data ecosystem where any mistake can intercept this process and causing data leak.

Replay attack just takes advantage of this hole and become a great threat in people’s Internet life.

A Replay attack can be also named as Repeat attack or Playback attack. This kind of attack is quite dangerous because it is hard to be detected and that can happen everywhere and anytime.

This is a network attack so we also call it replay cyber-attack, in which attackers can maliciously or fraudulently repeat or delay the valid data transmission, so that your data can be intercepted or re-transmitted by your adversaries or attackers without your knowledge.

an attack on a security protocol using a replay of messages from a different context into the intended (or original and expected) context, thereby fooling the honest participant(s) into thinking they have successfully completed the protocol run.


There are some commonly used types for Replay attack:

Network replay attack – the network can be easily intercepted by others and resent.

Wireless replay attack – the wireless communication can be blocked and resent by attackers.

Session replay attack – the session can be intercepted by hackers and user’s unique session ID, stored as either a cookie, URL, or form field, will be stolen.

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Examples of Replay Attacks

To make sure you have understood the meaning of Replay attack, we will enumerate some examples for you.

Try to image that, Amy wants to log in to her account through the Internet, whether her bank account or some social media accounts, so she enters the website and input her username and password to send the request for login. When the login request is accepted by the bank’s server or others, she can get what she wants.

But in the whole process, data transmitted through the Internet. An attacker is spying and monitoring the network. When he finds this loin request send by Amy, he quickly captures that and wait until Amy has logged out of her account.

All these happen without any traces. Amy can’t tell her account has been at risk even though she set her login credentials with high security level.

When the capture succeeds, the attackers can retransmit the captured login request to the server and once the server accepts it, the hacker can access to Amy’s account.

According to this example, you can tell why we stress the danger of this attack. It is hard to detect but people have developed some methods to prevent that.

How to Prevent Replay Attacks?

According to the working principle of Replay attacks, the main point lies in that the server can’t identify if the request is send from the real owners.

In this way, you can tag each encrypted component with a session ID and a component number and these components are independent to one another. While every time when the program runs, a unique and random session ID will be created, which makes the previous run hard to replicate and the Replay attack won’t work.

Just like such a work principle, there are some methods used to do the same thing to prevent replay attacks.

One-time passwords – this kind of password will expire after being used or just after a short period of time.

MAC (Message Authentication Code) – a short information can authenticate a message used to confirm that the message came from the stated sender and not changed.

Timestamp – it provides a temporal order among a set of events and ensuring that the data is only considered valid within a specific time frame.

Secure communication protocol – such as SSL, TLS, and IPSec, they can ensure the authenticity and correctness of transmitted data.

Apart from these techniques, it is important to keep your system up to date and use antiviruses and firewalls to prevent other cyber-attacks.

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Bottom Line:

This article has clarified what a replay attack is and if you still have related questions, you can leave your comments.

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