How To Prevent A Replay Attack in 2021

Ajay Ohri


Security and data breach is widespread these days, and businesses are more prone to replay cybercriminals attacks. They penetrate the system by unauthorised methods and access sensitive information that is not meant to be shared. The attacker could be anyone, a real person or even a program, or in the form of a virus or malware. This security breach is done to either gain information for personal purposes, intentionally crashing the system, or utilising computer resources for individual work.

The majority of the organisations plan for this security breach by adding intrusion detection programs, creating an incident response plan, creating a backup for data, conducting frequent penetration testing, and creating an Incident Response Team (IRT).

First of all, let us understand what the replay attack is.

  1. What Is a Replay Attack?
  2. How Replay Attack Works
  3. Ways to Prevent Replay Attack
  4. Knowing the Method of Replay Attack

1) What Is a Replay Attack?

A replay attack is a type of network-based security attack in which the attacker delays, replays, or repeats data transmission between the user and the site. The replay attack in network security is considered lethal because it can resend the message and fool the receiver without decrypting it. Here, the receiver might think that the news is genuine and legitimate.

The successful replay attacks in network security allow fraudsters to impersonate genuine customers and perform account takeover manoeuvres. It affects businesses negatively, as it tends to lapse in network security, causing companies to have friction with existing customers.

2) How Replay Attack Works

Let us understand replay attacks in detail with the help of a real-life example. Consider a company staff member asking for a financial transaction to the company’s financial administrator. He does so by sending an encrypted message. 

An attacker looking for a loophole to launch a replay attack might eavesdrop on this message to fulfil his intention. His next step would be capturing the message so that he can resend it. Now the message will look utterly authentic because it has already been sent once. The financial administrator, who receives the message, will find it legitimate as it has already been encrypted.

What will happen now? In this case, the chances are that the financial administrator will respond to this new message unless there is a strong reason to get suspicious. He will not differentiate between the two statements— the one he received from the company’s staff member and the other he received from the hacker. 

The receiver, in this case, the financial administrator, has received the same message. It could lead to the financial administrator sending a hefty amount to the bank account of the attacker.

So, what the hacker did was capture the message from the network and decrypt it. He doesn’t even require reading or deciphering the message. He just resends the news as it is.

The attacker used a simple technique or hack to break into the system and replay it only by resending a message. It is how a replay attack in network security works. 

3) Ways to Prevent Replay Attack

Now we have understood the consequences of replay attacks in network security and the type of loss they can incur to organisations. The next step is preventing networks from such replay attacks and keeping the company’s assets safe.

Many companies have devised specific ways and means for preventing replay attacks in network security. They are looking for a robust solution to prevent fraud and leverage fraud analysts to detect such suspicious events and replay attacks fast.

The most important aspect of preventing replay attack is having the right kind of encryption. If the messages are encrypted, then they carry a code or key with them. These messages only get opened when these keys are decoded.  

In case of a replay attack in network security, the attacker doesn’t need to read or decipher the key or code. He or she just has to capture or resend the entire message along with the key.

So how to best counter this possibility? There are various methods by which replay attacks and the impact of cybersecurity breach could be prevented :

  • Identifying the company’s IT assets

It is essential to identify all your IT assets because you will not protect your network if you cannot identify them. That’s why a complete audit of the entire IT assets must be performed from time to time so that these resources can be protected from malware replay attacks. This way, you can also replicate as part of recovery.

  • Adding an intrusion detection system

It is crucial to identify and spot a data breach. Because without identifying, you will not be able to ensure a quick response to minimise the damage and avert the risk. It is also essential for making risk mitigation easier and recovery better. 

With the help of an Intrusion Detection System (IDS), you can identify and be informed whenever any security breach occurs. It will help you to respond to them at the earliest. Then there are advanced Intrusion Prevention Systems, which automatically trigger network breach response measures. It lets you contain the replay attack in network security immediately. 

One more type of IDS is Security Information and Event Management (SIEM) systems. If there is any network hacking attempt, you can easily collect all the relevant information through SIEM. It will help you get to know about the replay attack methodology. It is quite useful for the prevention of future replay attacks.

  • Creating an incident response plan

The Incident Response Plan (IRP) is a document that charts out the responsibility of each person in the organisation in response to a replay attack in network security and breach of security. If an organisation’s IRP is in place, then employees will be able to react faster. This method is beneficial for containing data breaches and eliminating them more quickly. 

The document must be distributed to every employee of the organisation to understand it properly and meet the document’s expectations. Employers must give employees proper training sessions or meet them often to make them know how they should meet their expectations.

Every employee’s role in the document must be stated clearly, even if it reports the incidents to critical stakeholders.

  • Creating a data backup

The best way to avert a cyberattack is by creating a remote data backup of the essential information. This way, you will restore the local files if any network breach occurs and prevent data loss from breaches that can encrypt and damage locally stored files. 

It comes under Disaster Recovery (DR). For creating a backup, the organisation must first categorise all the data. It will help the organisation to preserve important information in an emergency. If the companies follow simply copying the entire data, they incur unnecessary expenses because it requires extra storage.

  • Conducting penetration testing at frequent levels

Penetration tests act as an essential tool for mitigating risk and identifying vulnerable assets in an organisation while preparing for security. It helps organisations to fix any breach even before it occurs. 

It is a mock cybersecurity attack in which experts break into a company’s cybersecurity architecture to test and identify the entire network’s potential loopholes. Once found, those loopholes can be fixed before actual attackers leverage them for penetrating the system. 

Organisations do these tests every time any modification is done to the IT hardware or software.

  • Creating an Incident Response Team

In the point mentioned above, we have seen how important and useful it is to have an organisation’s incident response plan. Similarly, it is equally beneficial to have an Incident Response Team (IRT), a team with the right set of skills and experience to handle the response in case of a security breach. 

Organisations can form an Incident Response Team, either from their own internal IT staff or from a third party staff provider. These people will ensure that the IRP related work is carried out properly without much hassle. The people deployed in this team’s main job will be collecting, analysing, and acting on the information related to security incidents. 

This team is referred to as the Computer Security Incident Response Team (CSIRT) in many organisations. Apart from incidents like data or network breaches, they also deal with other incidents.

  • Responding to a security breach

When you identify that there has been a security breach owing to a replay attack in network security, your organisation’s first step should be to have a clearly defined plan of action ready. Organisations can take an incident response plan as a guide in case of any such situations. 

Organisations must share the entire plan with all their employees to be aware of their roles and responsibilities if a cybersecurity replay attack occurs.

  • Recovering from a breach – stopping the replay attack

Once you identify that the security breach has occurred, what will be your first step? Yes, the first step of any organisation will be recovery. The faster a company can recognise the data breach, the better they will plan the road to recovery. The reason is simple; every attacker takes time to get through the first system they have compromised, and only then can they get through the rest of the network.       

The second most crucial step is in containing the breach. The best way to do this is entirely cut off the attacker’s access to the system. It could be done by isolating the system that has been compromised. One can even revoke the user’s access to the system that has been attacked.

Now that you have successfully contained the threat, the next step should be to eliminate it. Organisations can use various means of eliminating the threat, depending on the type of breach. 

A replay attack, a form of ransomware, will require completely formatting all the affected data storage media. Even physically removing and replacing data to remove the system’s ransomware. The organisation can quickly restore the data that has been destroyed from a remote backup.

By identifying, containing, and eliminating a breach before the attacker breaks out of the system they compromised, the organisations can minimise the damage they caused to the system. The recovery process will start to post after the replay attack’s actual or original source has been eliminated.

4) Knowing the Method of Replay Attack

If organisations know how the replay attack has been planned, they will prevent the attackers from repeating the same strategy. Another method is investigating the impacted system to get clues or signs related to compromise further. It is quite a possibility that the attacker must have left other malware on the system when they had access to the system.

For best practice, organisations should save the activity logs of the time of the breach for further forensic analysis. With the help of these activity logs, organisations will get to know the source of a replay attack, and they will be able to block future attempts.

Notifying the Employees Affected by the Replay Attack in Network Security

Once you can conclude which systems have been compromised and what data has been put at risk, your first step should be to inform everyone by sending notifications that the replay attack security breach has impacted. The faster any organisation can send the notifications, the better it is. It could be emails or phone messages, details like the breach’s date, the kind of files compromised, and what steps are required by the recipient to protect themselves must be captured in the notification.


Replay attack in network security is quite dangerous, as it involves many advanced skills. If organisations use the processes and methods mentioned above to preserve their essential IT assets, then protecting data from any attackers or hackers will not be difficult.

So, have you made up your mind to make a career in Cyber Security? Visit our Master Certificate in Cyber Security (Red Team) for further help. It is the first program in offensive technologies in India and allows learners to practice in a real-time simulated ecosystem, that will give them an edge in this competitive world.



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