Over the years, Microsoft has issued over 700 upgrades to Windows XP and about 60 percent of those updates were rated as "critical." Given its track record, there's a good chance more vulnerabilities will be discovered and that could cause a big headache for companies and consumers still using the outdated OS, said Sanjay Castelino, vice president of marketing at Spiceworks, a professional network for IT.
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"It opens up the possibility for a big negative impact. It's not like everything is going to blow up right away, but as of Tuesday they are not issuing fixes," Castelino said. "So you might find two months from now, people are complaining because a problem arises and now as a business you are under the gun to resolve that problem with very little time to do it."
Windows XP was released to the public in 2001, and despite newer operating systems since then (Windows 7 in 2009, and Windows 8 in 2012) a lot of businesses still use it to run important operations.
According to a recent Spiceworks survey, 76 percent of respondents said they still use at least one Windows XP system on their network, a statistic that Castelino called "scary." And the system isn't just limited to office computers and personal computers, it has also become common on ATMs, point-of-sale retail devices and even in some health care equipment.
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Because the software is so widespread, it can be difficult for companies to ensure they are 100 percent protected. Even if a business has actively been upgrading all outdated systems, there's still the chance that it could miss some machines, and that can cause a lot of damage, said Ken Bechtel, a malware analyst at Tenable Network Security.
"There could be a lot bigger impact than people are realizing," Bechtel said. "A lot of companies aren't sure of which computers are running XP and which aren't. It's hard to get that kind of transparency."
Companies still using the software are doing so primarily because of the cost of switching operating systems and because apps that are critical to their business weren't compatible with later systems, Castelino said.