The Justice Department has said it will investigate “whether and how” online platforms in “search, social media, and some retail services online” are engaging in behavior that stifles competition and harms consumers. While the Justice Department did not name any targets in announcing the probe on Tuesday, sources have indicated Alphabet Inc’s Google, social media giant Facebook Inc, online retailer Amazon.com Inc and possibly Apple Inc will likely be reviewed. Here’s what regulators could focus on at the big technology companies: