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Information security for text messages, emails and letters

Use a practical approach to information security, one that balances a user’s need to be kept informed with being kept safe.

Contents

Start with user needs, not government needs

Start by writing the message you want to send. Don’t worry about the information security aspect just yet – write the message you want to convey as clearly and directly as possible.

Use our design patterns along with the GOV.UK style guide to help you write clearly and convey the right information at the right time.

Once you have a message which meets user needs, look at it in relation to the risks we outline. Use this to decide if you need to change the message in order to keep the users safe.

Understand the risks

There are 3 main risks involved in sending notifications by text message, email or letter:

  1. Someone accidentally sees the notification.
  2. An attacker intercepts a message, or gains access to someone’s email inbox, phone messages or paper files.
  3. An attacker tricks the user by sending a fake notification (phishing).

Someone accidentally sees the notification

For some messages, the recipient would be unhappy if someone else accidentally saw the contents, for example, the results of a recent medical test.

This is a privacy issue – in this case the unintended recipient isn’t trying to steal money or identity information.

To address this risk, don’t reveal the important information in the subject line or opening sentence, or ask the user to sign in to see the information in full.

An attacker intercepts a message, or gains access to someone’s email inbox, phone messages or paper files

It’s possible for hackers to intercept messages. Text messages, emails and letters can all be intercepted.

It’s also possible for a criminal to gain access to someone’s entire email inbox, phone messages or paper files. Email accounts can be hacked, phones and paper files can be stolen, left lying around or picked out of the rubbish.

In both cases, criminals are looking for information they can use to commit fraud. To address this risk, don’t send payment details, ID numbers or any other information that can be used for fraud.

An attacker tricks the user by sending a fake notification (phishing)

In this scenario, a hacker sends lots of messages pretending to be from an official government service, hoping to trick someone into revealing information of value.

This is known as a ‘phishing attack’.

To address this risk, don’t send requests for personal information of any kind, unless the request is directly connected with a transaction.

Information security principles

Protect the user’s privacy

To avoid someone other than the recipient accidentally seeing a message that has sensitive or confidential information, either:

  • use a generic subject line and opening sentence, and only give the information in full within the body of the message
  • send a generic message which asks the person to sign in to see the information in full

Remember that even the sender ID also reveals information. For example, don’t set your sender name as ‘STI clinic’.

Don’t send information that can be used for fraud

To reduce the risk if messages are intercepted, hacked or stolen, don’t send messages with:

  • payment details
  • passport, driving licence, or National Insurance numbers, or any other personal ID numbers
  • the person’s date of birth, mother’s maiden name or other information commonly used for identification
  • the person’s full address or previous addresses
  • passwords (c’mon team)
  • payment amounts – if you use them as a form of identification

Payment details can be used for fraud straight away. Other information requires a bit more work. For example, an attacker might use one piece of information to get hold of another, eventually gaining enough information to commit fraud. Or a criminal might use information from several old messages to steal someone’s identity.

Don’t send requests for personal information of any kind, unless the request is directly connected with a transaction

To reduce the risk from phishing attacks, don’t send requests for personal information of any kind, unless the request is directly connected with a transaction.

It’s OK to send a request for personal information if it’s directly connected with a transaction. For example it's OK to send a notification with a link asking users to reset their password if they've requested it by clicking on a ‘Forgot your password?’ link.

The same rules apply to links:

  • Don’t send links that reveal information that can be used for fraud.
  • Don’t send unsolicited messages that include a link requesting personal information of any kind (it’s OK to send a message with a link requesting information if the user has just requested it).

There are additional rules that apply specifically to links.

  1. Links must point to a .gov.uk domain – for example, https://www.gov.uk or https://www.armslengthbody.gov.uk.
  2. Links must show the URL in full – for example https://www.gov.uk/vehicle-tax, not gov.uk/vehicle-tax.
  3. Don’t use redirects or tracking links – disguising the URL makes phishing easier. Just show the URL in full.
  4. Don’t link directly to a sign-in page – this is a request for personal data. If the user needs to sign in to your service, link to your start page on GOV.UK.
  5. It’s OK to deep-link into your service, as long as the user doesn’t have to sign in to view the information or take action.

Don’t send attachments

If you want to communicate something, write it in the body of the email. This is more user-friendly. If the information is too sensitive to include in the email body, it’s too sensitive to include in an attachment.

If you need to send someone a file, make the file available within your service, then link to it.

Include the user’s name – it makes phishing more difficult

Start your message by addressing the user. For example, ‘Hi Alice Smith’, or ‘Dear Bob Jones’. Including this extra piece of information makes phishing more difficult.

Use technical approaches to improve privacy and prevent phishing

There are several technical approaches to preventing phishing. You must use SPF/DKIM, DMARC and TLS.

SPF/DKIM and DMARC make sure your emails get delivered, whilst phishing and spam email gets filtered into junk mail.

TLS makes sure that no-one can intercept your emails.

Examples

Example of an appointment reminder

“Dear Anne Smith, you’ve got a licence appointment tomorrow at 2:15pm at the Licence Office, 1 Chapel Hill, Heswall, Bournemouth BH1 1AA. To cancel your appointment, visit licensing.service.gov.uk/appointment/12345678/cancel. To change your appointment time, sign in to your account.”

This is a good example because:

  • the message and link doesn't reveal any sensitive personal data
  • it doesn't ask for personal data, passwords or payment details
  • the reminder addresses the user by their name, making phishing attacks more difficult
  • the link just cancels the appointment which minimises what an attacker can do
  • users have to sign in to change the appointment time, making it harder for an attacker to know what their appointment time is
  • the topic is something the user is familiar with

Example to add a photo to an environmental permit

“Dear Andrew Jones, to add a location photo to your environmental permit application, visit environmentalpermit.service.gov.uk/12345678/add-photo. If you didn’t request this link, please ignore this message.”

This is a good example because:

  • the message and link doesn't reveal any sensitive personal data
  • it doesn't ask for personal data, passwords or payment details
  • the reminder addresses the user by their name, making phishing attacks more difficult
  • the link only lets users add a photo to an environmental permit application – it doesn’t complete the process, which minimises what an attacker can do
  • it shows users what to do if the message doesn't apply to them

You can do more if you want to

These guidelines are the minimum requirement. You can take stricter measures for your service if you think it's necessary.

Just make sure you’re balancing your users’ needs to be kept informed and kept safe.

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