Bought a couple of new pen drives at a market in BKK a few weeks back. They have both set off my anti-virus program on numerous occasions. It appears they come with pre-installed malware/viruses. Has this happened to anyone else? It had never occurred to me this could happen.

Yes have had it happen. Be very careful with that virus. It will infect the first computer and then any other usb you put in. Make very sure you have fixed the issue before you use the drives on another computer. So not use them on any other machine. If its the USB virus. A scan of the drive and computer will show the virus being deleted and fixed when in some cases it is not. That tricks the user into using the pen in another computer and therefore infecting more. Bottom line you must be in safe mode find and stop the running process and fix with antivirus. Throw the drives away.

No wonder they were so inexpensive.

You may as well toss the pen drives.

Were they in bubble packs or loose?

Make sure you have Autorun turned off and install Panda USB Vaccine.

I bought this Chinese-made Hard Disk once, shrink wrapped, and they'd very kindly filled it with thousands of MP3s and music videos.

All Chinese though.

NEVER buy USB thumb drives from markets. They're cheap enough at Big C, Tesco....

buying a USB stick at a market ?

pay peanuts, get malware-monkeys me thinks.....

pay a few Baht more and buy a stick in a reputable store and from a reputable manufacturer in a blistered package

buying a USB stick at a market ?

pay peanuts, get malware-monkeys me thinks.....

pay a few Baht more and buy a stick in a reputable store and from a reputable manufacturer in a blistered package

And having owned dozens of PEN drives / USB sticks over the years I would recommend Kingston Data Travellers. Tukcom do them in the manufacturer's packing. They ARE more expensive but last longer so work out better VFM.

After all, how much is your data worth to you?

One other thing....I suggest formatting them before you use them, a full format, not a quick format. Sometimes the format is "iffy" and better to find out before you store data on them

Even that is no guarantee....

https://srlabs.de/badusb/

Even that is no guarantee....

https://srlabs.de/badusb/

Very true, I'd sort of forgotten that (!!) but by buying a device from a reputable manufacturer you minimise the risk. Also, if someone hands you a USB device and says "use this", consider who it is and how likely they are to be taking care of their systems!

This link http://community.norton.com/en/forums/does-norton-detect-badusb is interesting

Never happened to me because I have enough common sense to know, never to buy flash drives from a market.

There is no reasons to buy these kind of items from markets these days, the price of flash drives sold in the reputable stores have decreased greatly over the last couple of years, almost at give away prices.

The best thing the OP can do is scan and clear his computer of viruses and throw the offending device in the bin.

Last year there was a report saying Thailand was #1 in the world for malware and viruses. Even brand new machines were full of them.

If you don't know what you're doing on your computer and take it to a Thai shop, chances are high you are coming home with malware or a virus. That's just how they operate here.

that is how the virus got into the Iranian computers at the Nuke plant......

will a reformat take everything off a thumb drive ?

that is how the virus got into the Iranian computers at the Nuke plant......

will a reformat take everything off a thumb drive ?

NO Not BadUSB it won't!!!

Read Chicog and my links above in posts 9 and 10 and/or search BadUSB - it's rather worrying!