UK’s National Health Service database crashes after staff member accidentally sends email to 1.2 million people – how businesses can prevent email errors

Accidentally hitting “reply-all” to an email might lead to awkward responses or some laughs in the workplace – but it’s unlikely it would cause your entire system to shut down, which is exactly what happened the the UK’s National Health Service emails yesterday.

ITNews reports that an IT contractor at the NHS sent a blank test email to the entire staff database, consisting of 1.2 million recipients.

The email prompted a flurry of response emails, most questioning why they were placed on the list, and what the purpose of the email was. Due to the sheer number of responses in a short time frame, the email system crashed, according to reports.

One NHS IT worker said in a tweet that he estimated there to be almost 300 million “unwanted emails” in the system.

In a statement, a spokesperson for NHS’s digital team said that a number of email accounts were “operating slowly” due to a “bug in the supplier’s system”.

“As soon as the issue was identified, our supplier disabled the distribution list so that no-one else could respond to it. We anticipate that emails sent before the distribution list was disabled will soon stop being received and that the issue will be resolved,” the spokesperson said in the statement.

However before the shutting down could occur, a number of NHS staff members took to Twitter to ridicule and laugh about the situation, sending #nhsmail trending.

“If you think you’re having a bad Monday, a woman just accidentally emailed all 1.2 million NHS employees & crashed the whole system #nhsmail,” read one tweet.

One staff member reported that another staff member had attached a “read receipt” to their reply all email, requiring all 1.2 million recipients to confirm they had received the response.

Preventative measures for businesses 

Cyber security expert at Sense of Security Michael McKinnon told SmartCompany that large enterprise email systems often have systems to prevent this from happening.

“There generally are preventative measures to stop this from happening, as this sort of mishap happens an awful lot,” McKinnon says.

“Usually it’s via the CC or the BCC line, not via a massive reply-all chain.”

McKinnon says these events can be prevented by limiting who has the authority to send messages to all staff, with some email systems even requiring password authorisation before sending such emails.

“This was definitely an oversight from a configuration point of view,” he says.

The system crashed thanks to the email server effectively Direct Denial of Service (DDoS) attacking itself, causing the system to be overloaded beyond expected capacity.

“Email systems usually have the capacity to deliver one or two times their normal load, but I estimate this would have been upwards of ten times the normal load for their system,” he says.

“There was just an absolutely massive amount of emails being sent at once.”

McKinnon also highlights the privacy issue these scenarios can raise, with the potential of 1.2 million staff email addresses being accidentally shared around.

“If the emails have been delivered not in the CC line, what you’re potentially doing is giving out your entire staff’s email contact list,” he says.

“For other companies, these sort of mistakes could reveal entire client lists, or reveal everyone you’re doing business with.”

If businesses want to avoid this, McKinnon advises a degree of care with who has the capability to send emails to large databases.

“It’s best to limit who has access to the all staff distribution lists. Emails are costly in terms of time, and it’s best to minimise all unnecessary communication.”

“You have to have controls in place to stop this happening.”


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