More than 41,000 people working for the US Department of Homeland Security, including ICE agents, have had their details published online by a group of hacktivists.

As TechCrunch reports, the leaked records include the names, job titles, work email addresses, phone numbers, abd office locations.

More than half of the leaked records relate to US Customs and Border Protection (CBP) employees, typically found at airports, seaports, and land border crossings. Around 10,000 ICE employees have had their records breached, and almost 1,000 members of the Cybersecurity and Infrastructure Security Agency (CISA).

WIRED reports that the massive leak includes staff who work undercover, as well as in other sensitive areas such as those engaged in wiretapping and the interception of communications.

A hacktivist group calling itself "Department of Peace" says that the data was taken from an Okta single sign-on system that staff use to log onto the central network of the US Department of Homeland Security. Okta for its part says that it has not seen any evidence that its own systems have been compromised.

The data reveals which tools and services particularly individuals can access. Alongside everyday office software, these include Palantir's Falcon investigative platform, the phone and social media analysis tool PenLink, and Mobile Fortify, a facial recognition app used by immigration agents.

Explaining its justification for the data breach, "Department of Peace" wrote:

"They have our information, so it’s only fair that we have theirs."

The leaked data has been published online, under the title "Icepick", and can be either downloaded via a torrent or accessed via a web interface - making it significantly easier for curious parties to search.

One threat intelligence expert told WIRED that, if authentic, the leaked data was "an extraordinarily valuable intelligence resource for those seeking to penetrate DHS," and could help adversaries identify vulnerable personnel or compromise ongoing investigations.

An obvious concern is that the leaked contact details could be used in phishing attacks that target employees, or could potentially put agents in physical danger. Clearly anyone whose details have been exposed through the incident would be wise to treat unexpected emails, texts, and phone calls with caution - and be particularly wary of any communications that claim to come from IT support or ask for a login to be approved.

Earlier this year the same group of hacktivists claimed to have breached the US Department of Homeland Security and accessed contracts between DHS, ICE, and more than 6000 firms including the likes of L3Harris, Raytheon, Palantir, Microsoft, and Oracle.

Explaining their motivation for that breach, the hackers referred to the killings of Alex Pretti and Renée Good by federal agents in Minneapolis.

"Why hack the DHS? I can think of a couple Pretti Good reasons! I'm releasing this because the DHS is killing us and people deserve to know which companies support them and what they're working on."

There has been a long string of cybersecurity incidents affecting US government personnel. For instance, in September the notorious ShinyHunters hacking group claimed to have stolen personal details related to nearly every employee of the FBI, and the records of millions of serving and former US military personnel were reportedly stolen from the Pentagon's human resources unit.