If you think you’re avoiding the crush of holiday shoppers by doing your shopping online, you could be in for a surprise. You could actually be dealing with even tougher competition from automatic cyber shopping software.

If this year's best online holiday deals seemed to sell out too quickly, it may have been more than just bad luck. You may have been competing against powerful software dubbed "Grinch bots" by some analysts.

"We’re up against a formidable competitor with some of the bots now going out there are trying to steal the deals from us," says Scott Schober, who has authored several books on cybersecurity. "During prime shopping, there’s claims of up to 97% of online traffic on these shopping sites are by bots, which blows your mind."

Analysts say the bots can be programmed to sniff out and snap up discounted items, so they can be resold for a profit.

That's perfectly legal, but Schober notes that bots are often controlled by gangs of hackers overseas. He says the biggest worry is what else they're up to.

"They’re trying to steal our login and passwords – so the obvious concern is we have to make sure we have a good unique password for each site. Don’t ever reuse passwords because once they get one, these automated bots are going to try to use our password across multiple sites," Schober warns.

For added protection, you can look for the green lock in your browser, or the "S" in the web address - both mean that the website encrypts traffic.

And if you’re still looking for last-minute gifts, experts advise resisting the urge to overpay for this year’s hot sellers… or you could wind up doing business with a Grinch bot.