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Incident response planning: six steps for managing a cyber security breach
Discover how to react if a cyber security breach ever affects your company with this helpful six step guide. Learn how to act in response to a cyber attack, who to notify and how, and what your next steps should be.
October 27, 2025
5 minutes
The faster you react to a cyber security attack, the less damage and cost your business is likely to incur. Having an incident response plan, and regularly rehearsing it, will help to ensure you and your employees will be able to move rapidly.
As soon as you suspect a problem, disconnect (but don’t switch off) all devices. Document as much evidence as you can. Notify the National Cyber Security Centre, Action Fraud, the ICO, or any affected customers and partners, as relevant.
When you restart business activities: restore data from clean backups, change all your passwords, update all your software. Then learn from the experience by holding a review that results in improved security measures and an updated incident response plan.
1. Make it safe and contained quickly
As soon as you suspect a problem has occurred, be sure to do the following:
- Disconnect all affected devices from the internet and your internal network (but don’t switch them off unless an expert has advised you to do so).
- Change the passwords or disable access for any accounts you think might have been compromised.
- Use your firewall to block any internet domains or addresses that you suspect may be malicious.
Your immediate aim should be to prevent the attack from spreading any further within your business, without destroying any evidence.
In the first hour of a cyberattack, your best investment is time: contain safely, capture evidence, report early. Those three actions will determine how fast you recover – and how much it costs.
2. Document everything
Immediately start an incident log and record everything that’s relevant. It should include the following information:
- Who discovered the incident.
- A timeline of what happened.
- The systems and users affected.
- The indications that these have been compromised.
- The actions you have taken.
Doing this will speed up the notifications you need to make (see step 3), as well as help to expedite any insurance claims. It’ll also improve your post-incident review (see step 6).
Depending on the kind of attack that has happened, you will need to report to at least one, but maybe all, of the following organisations:
- For significant cyber incidents, the National Cyber Security Centre (NCSC). Note that this does not replace mandatory reporting to the ICO (see below).
- If people’s personal data is involved, GDPR states that you must notify the Information Commissioner’s Office (ICO) within 72 hours.
- For fraud and cyber-crime incidents, Action Fraud (which is run by the police).
Note that the UK government does not condone making payments in the case of a ransomware incident, a policy we strongly agree with here at BT.
4. Notify customers and partners
If the cyber attack involves the loss or theft of personal data belonging to your customers, GDPR says that you must notify those affected as soon as possible.
You should also notify any other organisations that your business partners with, such as suppliers or clients, if they are also affected.
Here, it’s important to act proportionately. As part of your incident response planning, prepare a factual statement that you can send out. It should explain what happened, what you’ve done and what the people reading it should do. Above all, don’t speculate on anything you don’t know for sure, and don’t make any promises.
5. Get the right experts on board
6. Recover and learn
Once the dust settles, you can start to get things back up and running.
- Ensure you restore data only from clean, unaffected back-ups.
- Change all your log-in credentials.
- Patch any vulnerabilities that may have caused the incident (such as software that hadn’t been updated).
Then conduct a post-incident review to clarify what happened and how. For this to be a useful learning exercise, it should result in a set of actions, each with an owner who’s responsible for carrying it out.
An effective review will also enable you to improve your security measures and incident response plan.
Key takeaways
If you only remember three things, make them these:
- Prepare a documented incident response plan where it’s clear who needs to do what and when.
- Act rapidly as soon as you suspect a problem: respond decisively and report early.
- Hold a post-incident review to learn from what happened. Use it to help your business improve its security and incident response plan.
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