The Red Cross says it was the victim of a sophisticated cyber security attack.

The organization says the attack, which was detected this week, compromised the personal data and confidential information of more than 515,000 "highly vulnerable people."

Those people include families separated due to conflict, migration and disaster, the organization says. Information about missing persons and people in detention was also jeopardized, according to the Red Cross.

"We are all appalled and perplexed that this humanitarian information would be targeted and compromised," said Robert Mardini, International Committee of the Red Cross' director-general. "This cyber-attack puts vulnerable people, those already in need of humanitarian services, at further risk."

The organization says it doesn't know who carried out the attack, which targeted a company in Switzerland that is contracted to store data for the Red Cross.

Mardini is asking the cybercriminals to spare the vulnerable people whose information was compromised.

"Please do the right thing. Do not share, sell, leak or otherwise use this data," he said.

He added that the Red Cross is working to understand the scope of the attack and take actions to protect against future security breaches.