The U.S. Federal Trade Commission opened a broad antitrust investigation into Microsoft, a source familiar with the matter said on Wednesday, making it the latest Big Tech firm to come under scrutiny from regulators.

The FTC would be looking into its software licensing, cloud computing businesses, and practices related to cybersecurity and artificial intelligence products, the source added.

Here are some key cases against Big Tech:

Microsoft

The FTC's antitrust probe was approved by Chair Lina Khan ahead of her likely departure in January and the expectation that incoming President Donald Trump would appoint a fellow Republican with a softer approach toward business.

The antitrust investigation into Microsoft would also look into allegations that the software giant is potentially abusing its market power in productivity software by imposing punitive licensing terms to prevent customers from moving their data from its Azure cloud service to other competitive platforms, sources confirmed earlier this month.

Alphabet

In Alphabet's Google search case - where a federal judge ruled that the company broke the law with an illegal monopoly on online search - prosecutors argue that it should sell its Chrome browser, share data and search results and possibly even sell Android.

In December, Google will have a chance to propose its own remedies, after which U.S. District Judge Amit Mehta will hold a two-week trial on what remedies are appropriate in the case.

Separately, Google was in February hit with a 2.1 billion euro ($2.22 billion) lawsuit by 32 media groups, including Axel Springer and Schibsted, alleging that they had suffered losses due to the company's practices in digital advertising.

In the same month, Google asked a U.S. judge to throw out a jury verdict in a lawsuit by "Fortnite" maker Epic Games that found the technology giant had abused its market dominance in setting rules for its app store.

Epic Games had prevailed in the high-profile antitrust trial that if it holds could upend the entire app store economy.

Apple

In March, the U.S. Department of Justice and 16 states sued Apple alleging the iPhone maker monopolised the smartphone market, hurt smaller rivals, and drove up prices. The DOJ has been probing Apple since 2019.

The California-based firm is also under regulatory scrutiny in Europe. It is set to be fined by the European Union's antitrust regulators for breaching the bloc's tech rules, Reuters reported earlier this month.

The European Commission in June determined that App Store's rules breach the Digital Markets Act - new rules for Big Tech firms.

Earlier this year, Apple was hit with a 1.84 billion euro fine for thwarting competition from music streaming rivals through restrictions on its App Store. Apple is appealing the penalty.

Other lawsuits include a class action filed in March in San Jose, California federal court accusing the company of monopolising the market for cloud storage in its mobile devices.

Meta

Meta must restrict the use of personal data harvested from Facebook for targeted advertising, Europe's Court of Justice of the European Union court ruled in October.

This came after privacy activist Max Schrems took his grievance to an Austrian court and said he had been targeted by advertisements as a result of Meta's personalised advertising based on processing personal data.

Earlier in June, the European Commission notified the company that its "pay or consent" advertising model, already the target of privacy regulators and activists' ire, was in breach of the DMA.

An appeals court ruled in March that Meta cannot stop the U.S. Federal Trade Commission from reopening a probe into its Facebook unit's privacy practices for now. The company had objected, citing the $5 billion fine it paid and the range of safeguards it had agreed.

In October last year, dozens of U.S. states sued Meta and its Instagram unit, accusing them of fueling a youth mental health crisis by making their social media platforms addictive.

The company was hit with a record 1.2 billion euro fine by its lead European Union privacy regulator in May 2023 over its handling of user information and given five months to stop transferring users' data to the U.S.

Amazon

The FTC filed a long-awaited antitrust lawsuit against Amazon.com in September, charging the company with harming consumers with higher prices.

While some of the states that sued alongside the FTC had their claims dismissed, the case was to still go forward to pursue any claims the judge did not permanently dismiss, as of October.

The FTC has also filed other lawsuits against the company, including one accusing the e-commerce giant of duping "millions of consumers" into purchasing subscriptions for Prime services.