Big tech companies hired aggressively during the last financial crisis, and they're doing it again. Here's what Apple, Google, Amazon, and Facebook are looking for.

The social networking company is hiring "at a very, very aggressive clip," COO Sheryl Sandberg told CNBC Thursday.

Facebook has seen a spike in traffic since the coronavirus outbreak, and most of the new hires will be in product and engineering teams, the company said.

Facebook is also continuing to ramp up its efforts to combat misinformation in advance of the US presidential election in November, and will hire new workers to its legal and global operations teams.

Google currently has over 3,000 open positions listed online. Many have been posted in the last week, including roles like software engineer and program manager.

Laszlo Bock, a former Google HR head, told The Journal that Google had previously taken advantage of economic downturns to make some of its key hires, like in the dot-com bust 20 years ago.

"If you have a lot of resources and you're hiring and other companies are struggling, that's when you pick off the right people," Bock, who is now CEO of workplace culture startup Humu, said. (Humu recently announced layoffs and job cuts.)

Amazon has already announced that it's hiring at least 175,000 new employees in warehouses and logistics to meet the rising demand for delivery amid the coronavirus crisis and stay-at-home orders.

In addition, the company has over 20,000 open tech jobs listed on its site, primarily for software developers, solutions architects, and IT support workers.

Apple has listed new jobs in the past month including for software engineers and product managers.

The company took advantage of the 2008 financial crisis to hire aggressively. Citing unnamed sources close to the company, The Wall Street Journal reports that CEO Tim Cook has told staff that Apple plans to do the same thing again in the coming months.

The company has also expanded perks for its Apple Store workers, who have been on paid leave since the company closed all its North American stores indefinitely last month. Apple has also been training its retail employees to work from home on repairs and technical support.