Difficult to add explosives to phones

Josep Jornet, a professor of electrical and computer engineering at Northeastern University and the associate director of the school's Institute for the Wireless Internet of Things, says it's also important to note that the technology used in pagers is very old.

If you opened an old electronic device, for example, Jornet says you'd be able to see most of the components and potentially add something by hand.

But with a smartphone, he says just opening it can be a challenge as it's sealed to be waterproof. However, once opened, you'd find many black chips, or integrated circuits on a piece of silicon. 

"It's very hard to to do something to a phone at that level with your hands without someone noticing," he said. "So it's going to be very difficult to add explosives to your phones."

However, Jornet did say that it would be possible for highly skilled individuals to take control of your phone remotely, whether or not there's an explosive inside. 

Once they have control, they may be able to send unwanted images and messages from your phone or wipe it clean, Jornet says, but that doesn't mean they could make the device explode, unless they had already physically manipulated it. 

"Even if you say, 'But maybe they can do something so it overheats.' All the phones today have failsafes that even if they get really hot, they will just switch off."

Phone supply chains more secure

Richard Forno, assistant director of the University of Maryland, Baltimore County's Center for Cybersecurity, suggested people can trust that their smartphones haven't been tampered with because the supply chains and manufacturing processes for them are much more secure.

For example, he says Apple doesn't give a contract out to just any company in China. According to Forno, Apple would require these companies to have due diligence, proper security, employee vetting and a host of other measures. 

"Apple actively monitors every step of the manufacturing process, which includes randomly testing what comes off the assembly line," Forno said.

He noted that for those in the West, the security of the supply chain is not a huge concern. However, if someone buys a phone from a back-end dealer off a shady website, he says it would be difficult to know where they're sourcing their materials from.

"That might be a cause for concern. For the average person, their iPhone, their Pixel phone, I have faith in the supply chain overseen by Google and Apple."

How to protect your phone

Still, Karimipour says that despite the low probability of our phones becoming dangerous explosive devices, there are actions people can take to ensure smartphones won't be compromised.

Most importantly, she says, people need to stick with established manufacturers and trusted retailers.

"Generally, trusted companies have better quality control and it's more likely to detect if there is any tampering."

She says it's also important to regularly update the software on your phone and to use security features like multi-factor authentication, where users must provide a password and additional identity verification like a fingerprint, to gain access to their device or accounts. 

Taking these basic security steps makes it more difficult for outside actors to gain remote access to your devices, she says, noting that it's also important to keep your phone in a secure place and take good care of it so that "no one can physically manipulate it or remove the battery."