Members of ISIS have taken to using encrypted messaging apps like Telegram and WhatsApp to sell their sex slaves.

The Associated Press reports that members of the extremist organization post advertisements for sex slaves next to ads for weapons, drugs, and other items. These auctions are held right in the open — it’s not hard for someone with ties to ISIS to find what they’re looking for.

ISIS holds an estimated 3,000 Yazidi women and girls as sex slaves. The group’s interpretation of Islam allows its members to take these slaves in what the New York Times calls an enshrinement of a “theology of rape.”

It’s not surprising that ISIS members would turn to encrypted apps to sell their slaves. The group is often lauded for its technical prowess: It uses drones to survey battlefields, recruits via social platforms like Twitter, and communicates using secure messaging tools like Telegram.

The AP says that ISIS focuses its attention on Telegram. Even though it has been criticized for developing its own cryptographic tools — Johns Hopkins University professor Matthew Green likened it to building a submarine out of Saran Wrap — it’s still popular among jihadists.

But the hard part isn’t finding out how ISIS perpetrates these vile crimes — we’ve known for almost a year that the group is fond of Telegram. No, the hard part is figuring out what anyone’s supposed to do about it without also undermining the privacy of people who aren’t using secure communications tools to engage in slavery.

While ISIS prefers Telegram, the AP reports that it also uses WhatsApp and Facebook to sell its slaves. WhatsApp uses the Signal protocol (which is also used by an app called Signal) to encrypt messages between its users. Facebook is said to be considering encrypting its Messenger service.

Encryption doesn’t care how it’s used

Both of those tools are used by a billion-plus people who have nothing to do with ISIS. Their shift to end-to-end encryption is a privacy boon for everyone — it means that communications are more secure against hackers, jealous lovers, and surveillance dragnets cast by intelligence agencies. Encryption doesn’t care how it’s used; it protects journalists, activists, and extremists in exactly the same way.

These tools shouldn’t go away because they’re being misused by a relatively small number of people. Yet something must be done about them; ISIS shouldn’t be able to openly sell another human being on the digital market. So what are the companies offering these tools supposed to do?

Right now they’re just deleting accounts. “We have zero tolerance for this type of behavior and disable accounts when provided with evidence of activity that violates our terms,” a WhatsApp spokesperson told the AP. “We encourage people to use our reporting tools if they encounter this type of behavior.”

Telegram, on the other hand, often deletes public channels used by ISIS. Neither option is a permanent solution, as they simply require ISIS members to sign up for new accounts or make new channels to communicate with each other. It’s a game of digital whack-a-mole where the stakes are higher than ever before.