According to American sportswear giant Under Armour, user data from its health app MyFitnessPal has been compromised. Data including the usernames, email addresses, and scrambled passwords from approximately 150 million accounts was stolen last month in one of the biggest attacks of its kind.

Thankfully, information such as social security numbers, driving license numbers, and details from payment cards aren't collected by the app, but email addresses and passwords alone have the potential to cause harm in the wrong hands. Under Armour hasn't commented on how the hack was carried out but says it's currently cooperating with the police and data security firms.

Shares dropped 3% as the company released a statement to investors informing them of the breach and assuring them necessary steps were being taken to tighten security. A notice to users was also issued, along with an FAQ page designed to separate fact from fiction and ease some fears.

Users have been urged to change their passwords on other accounts where the same passphrase and username/email address combination has been used as on MyFitnessPal. It's also a time to be overly cautious of any emails asking for personal data or sharing links or attachments. In other words, be very vigilant for the foreseeable future.