
Nobody's Cellphone Is Really That Secure, Bruce Schneier Reminds (theatlantic.com) 80
There are two basic places to eavesdrop on pretty much any communications system: at the end points and during transmission. This means that a cellphone attacker can either compromise one of the two phones or eavesdrop on the cellular network. Both approaches have their benefits and drawbacks. The NSA seems to prefer bulk eavesdropping on the planet's major communications links and then picking out individuals of interest. In 2016, WikiLeaks published a series of classified documents listing "target selectors": phone numbers the NSA searches for and records. These included senior government officials of Germany -- among them Chancellor Angela Merkel -- France, Japan, and other countries.
Other countries don't have the same worldwide reach that the NSA has, and must use other methods to intercept cellphone calls. We don't know details of which countries do what, but we know a lot about the vulnerabilities. Insecurities in the phone network itself are so easily exploited that 60 Minutes eavesdropped on a U.S. congressman's phone live on camera in 2016. Back in 2005, unknown attackers targeted the cellphones of many Greek politicians by hacking the country's phone network and turning on an already-installed eavesdropping capability. The NSA even implanted eavesdropping capabilities in networking equipment destined for the Syrian Telephone Company. Alternatively, an attacker could intercept the radio signals between a cellphone and a tower. Encryption ranges from very weak to possibly strong, depending on which flavor the system uses. Don't think the attacker has to put his eavesdropping antenna on the White House lawn; the Russian Embassy is close enough.