The Finnish Communications Regulatory Authority (FICORA) is looking at how many mobile phone SIM cards in Finland use encryption technology that may make them vulnerable to hackers.

The New York Times reported on Sunday that a German mobile security expert says he has found a flaw in the encryption technology used in some SIM cards that could enable cyber criminals to take control of a person’s phone.

Exploiting a flaw in the technology, a hacker could possibly send a virus to the SIM card through a text message, giving access to phone calls and purchases through mobile payment systems.

The expert, Karsten Nohl of Security Research Labs, estimates as many as 750 million phones may be vulnerable to attacks.

The Finnish Communications Regulatory Authority (FICORA) is to investigate how many vulnerable SIM cards may be in use in the country. The Finnish mobile operators Elisa and DNA say that SIM cards open to this kind of attack are not in use on their networks.

Mikko Hyppönen, Chief Research Officer of Finnish internet security company F-Secure, told Yle on Monday that there is no serious cause for concern over the reported findings.

“This type of attack does not affect all SIM cards. The brand or model of mobile phone doesn’t matter. The type of vulnerable SIM card could be in an iPhone or an Android phone or a Windows phone and the attack could be successful. In practice, no attack is underway and no one needs to be worried. But, this type of security hole has been discovered and action is starting to correct it,” Hyppönen pointed out.