They collect our emails, store our bank details, we tweet and use Facebook on them. They are our bank vault, our confidante, and our guide.
Criminals use Wi-Fi connection to harvest passwords and other sensitive data from smartphones or computers - often giving their Wi-Fi hotspots fake names familiar to punters at cafes and in airports.
Many smartphones are set up to automatically leap on to available Wi-Fi hotspots and start downloading emails.
Forty per cent of mobiles sold this year have been smartphones - and this has been a bumper year for malware developers who have focussed their attention on smartphones.
Those running Google's Android system have been especially targeted.
Bitdefender's Catalin Cosoi said: "We have investigated applications for Android devices and basically, based on our statistics, we've seen a 2,000 percent increase of malicious applications compared to the last year...Our prediction is that in the following 6 months, we will have a 6,000per cent increase in malicious applications."
Smartphones are becoming the gateway for cyber criminals and cyber spies into sensitive personal data, industrial and state secrets.
"Once you have a smartphone, you probably can't go back to an older version of a phone now that you have access to a computer, social media, emails, pictures and so on. You sort of get addicted, so smartphones are becoming very important," Cosoi added.
"On the other hand, it's very, very easy to create malware for smartphones.
"Sometimes you can take a malicious part from one application and insert it into another and start propagating an application on the web. So smartphones are increasing and also, it's very easy to create malicious applications for smartphones," he added.(ANI)