Facebook and Whatsapp are among the most popular smartphone apps out there. These two programs also topped the list of most-used apps in a recent survey carried out on DW's social media pages. DW users also reported installing dictionaries, email programs and Google+ on their phones.

But privacy advocates argue it's with the communication apps like Facebook and Whatsapp in particular that users should exercise caution.

"Whatsapp is probably the biggest telephone directory in the world," warned Dirk Kuchel from Computerbild magazine. "They know where each user is, who they are, and who they're friends with."

The problem with the app, Kuchel says, is that it uploads the phone's entire contact list to the system, "and no one asks where they actually make their money."

The app charges users a small annual fee which doesn't even come close to covering the cost of sending billions of short messages every day via the Internet. Instead, says Kuchel, it's likely the company uses the data in some other way - possibly by selling it. "Money is no longer the main currency of the Internet today, it's data," he said.

Hackers get rich

It's not just the potential for companies to abuse data that has social media experts worried. Hacker attacks on smartphones and tablets, as well as on computers, are becoming increasingly frequent. Hackers are finding different ways to access mobile devices, exploit their computing power and get hold of sensitive data.

Journalist and Internet expert Robin Cumpl says many smartphone users are still too naive when it comes to managing their private information, making things far too easy for cyber criminals. He compares cyber security to road safety: "When the seatbelt was introduced in cars, people also said, ‘What the hell?' But nowadays it's normal to wear one."

He believes the generation that's growing up with smartphones should also handle their data on the web in a completely different way. And then there's today's 35 to 40-year-olds: "For them, dealing with their data on smartphones is still new in many areas," says Cumpl.

Every smartphone user should be interested in getting the highest possible security for their data, said Dirk Kuchel. "There are attacks from all sides - from the criminal scene and from an economy in which people unwittingly pay with their data. There are even attacks by the state."

The most recent example of governments using smartphone apps to snatch information involved the US National Security Agency and its British counterpart. In a revelation in late January, the New York Times reported that the intelligence agencies had stolen data from the game "Angry Birds," accessing players' age, location and sex.

The newspaper used documents leaked by the whistleblower Edward Snowdon. It isn't clear exactly what the NSA uses this data for. In another case it was discovered that the flashlight app, which has been downloaded more than 50 million times, sent users' personal information to third parties without their permission.

"They still owe people an explanation about what they need the data for," said Kuchel.

No failsafe protection

Robin Cumpl argues users need to be especially wary of free apps. "If there's a program that costs five euros, and a similar app from another manufacturer is free, most users will go for the free program," without thinking the app could siphon their data, he says. Data siphoning is certainly also a possibility with apps that cost money, but when downloading free programs, Cumpl advises users to question how the developer ultimately makes their money, and how they can afford to offer an app for free.

Unfortunately there's no way to protect a smartphone completely from data thieves. Antivirus apps for smartphones are nowhere near capable of warding off attacks, according to a test run by Computerbild magazine. The test couldn't find any programs on the market that could provide foolproof protection.

"Apple protects us from pictures of nipples and has a phobia of nudity," said Kuchel. "Instead of that, they should be looking at eliminating programs that have viruses."

Apple, however, faces a much lower risk of viruses than the competing Android operating system, which is much more widespread.

Cost vs. convenience

Robin Cumpl believes every Android smartphone should at least have anti-virus software. And to explain, he's going back to the car analogy.

"I'm not going to throw out an airbag if it doesn't protect me when a meteorite falls on my car." It's more important, he says, to keep your eyes open. "Use your brain and look at what the app allows to be released."

Users should also always take the time to read the terms and conditions. "They usually make you want to skirt around it, but you shouldn't," said Cumpl. Often this document will outline whether the developer uses the data for marketing purposes - so users who don't want their information going to third parties will know not to download the app.

According to social media experts, it's users' reliance on convenience that often gets exploited by app companies.

"With Whatsapp you can select friends and add them yourself, without allowing the company to automatically copy your entire contact list," Cumpl said, but this road takes a little more patience.

His conclusion? Users should always think twice about what data a program really needs to function. And, when in doubt, don't download the app.