Cyber attack on the grid or the banks: what it would mean at home

What a cyber attack would look like at home

On Mumsnet, the "prepping for internet outage, cyber attack" thread mixes two worries: losing power, and losing access to money. The good news is that a household doesn't need a special "cyber kit". At home, a serious cyber attack looks like problems you can already plan for:

• a power cut, if the attack hits the electricity system
• a bank you can't use, if it hits a bank or payment system
• a wave of scams, because criminals use any disruption

GOV.UK's Be Ready home page names cyber attacks among the emergencies that can disrupt the services we rely on.

What the National Risk Register says

The National Risk Register 2025 (Cabinet Office) sets out "reasonable worst-case" scenarios for planners. They're deliberately severe and they aren't predictions. Three are relevant here.

1. Cyber attack on the electricity grid (page 45). The worst case is a total failure of the national transmission system in winter: everyone without a back-up generator loses power at once and without warning, with knock-on effects on phones, internet, water, sewage, fuel and gas. On recovery, the register says small pockets would get intermittent power back within a few hours, a large share of demand within a few days, and full restoration could take up to 7 days, though some critical services could take months. It also says Great Britain has never had a nationwide loss of power, and that the likelihood is low.

2. Cyber attack on a UK retail bank (page 59). The worst case is an attack that takes one bank's systems totally offline for at least 2 days, with a partial outage for 2 more. It says the hardest hit would be vulnerable customers with only one bank account, and that the bank would likely face more fraud.

3. Technical failure at a major bank (pages 102–103). Not an attack, but the same effect: customers unable to see balances, make payments, use online banking or take cash from ATMs, with some disruption lasting weeks as backlogs clear.

The Bank of England says banks are required to identify their important services, set limits on how much disruption they can tolerate, and test that they can stay within them. That's work for the banks, not you. What you can do is make a few days without your usual bank or without power less of a problem.

Money: cash, a second way to pay, and records

Keep some cash. Be Ready says to keep a small amount of cash for essentials, because card payments and cash machines may not work in a power cut. It doesn't set an amount. Finland's official guidance says enough cash to buy essential supplies for a few days. Our emergency cash calculator helps you think it through.

Have a second way to pay. The NRR says people with only one bank account would be hit hardest. Finland's guidance suggests accounts with two different banks, with a card for each. That's Finnish advice, not UK advice, but the logic carries over: if one bank goes down, the other may still work. A credit card from a different provider can do a similar job (our suggestion, not official advice).

Keep records. If an outage costs you money (a missed bill, an overdraft fee), the Financial Ombudsman says to contact your bank first, explain what happened and what you want, and keep statements, receipts and emails. For card payment or direct debit complaints the bank must reply within 15 days (full answer within 35); for other complaints it has 8 weeks. If you're not happy, the Ombudsman can look at it for free and may ask the bank to refund costs or pay for distress and inconvenience.

Is the money itself safe? An outage means you can't reach your money for a while. That's different from the bank failing. If a bank does fail, the FSCS protects up to £120,000 per person, per bank (from 1 December 2025).

Scams: the bigger day-to-day risk

The Financial Ombudsman warns that fraudsters use bank outages to call people, pretend to be their bank and offer to help, in order to get their details. During any outage:

• Never give details to someone who calls you, however official they sound. Hang up and call the number on the back of your card.
• Don't click links in texts or emails about the outage. The NCSC says to forward suspicious emails to its reporting service.
• If you've lost money or been hacked, report it: Report Fraud on 0300 123 2040 in England, Wales and Northern Ireland, or Police Scotland on 101 (NCSC).
• Citizens Advice's consumer helpline is 0808 223 1133 (Be Ready).

Before anything happens: the 15-minute cyber check

Be Ready's cyber page and the NCSC give the same basics:

1. Secure your email first, with a passkey if offered, or a strong, unique password and 2-step verification.
2. Turn on automatic updates for phones, laptops and smart devices.
3. Back up photos and important files, and practise restoring them.
4. Use a password manager, which also warns you about breaches.

The NCSC also has a free questionnaire that gives you a personal action plan. Our guide to household cyber security goes step by step.

If the power goes too

If a cyber attack did cause a power cut, it would be a power cut. Everything in our guides applies: water, food that needs no cooking, a torch, a battery or wind-up radio, a charged power bank, warm layers. See how to keep your phone charged and how to reach family if the mobile network goes down.

Where official advice is thin

• We found no UK government page that tells households what to do if their bank is offline for days. The NRR describes the risk, the Bank of England page is written for firms, and the Financial Ombudsman covers complaints afterwards. The cash and second-account advice above comes from Be Ready (cash, for power cuts) and from Finland's official guidance.
• Be Ready's cyber page covers protecting your own devices. It doesn't cover a national attack.
• The NRR's likelihood scores are for planners. We don't turn them into odds, and you shouldn't read them as a forecast.

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Related guides

• Long blackout or cyber attack: keeping your household going
• Household cyber security: the official steps, in plain English
• How much cash should I keep at home?
• Will there be blackouts this winter? What the 2026/27 outlook says
• Broadband and phone outages: what to do, and how to prepare
• Power cut kit: what to keep in one box, and how long power cuts last

Free tools

• Emergency cash calculator
• Power cuts near me
• Fridge and freezer power cut timer (FSA times)

We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.

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