Every like, share and click you perform on Facebook is already being used to target you with content and consumer advertising, but experts warn that activity can also be used to subtly (and sometimes dishonestly) influence your political beliefs, especially with a federal election looming next year.

Some are already sounding the alarm in Canada about the potential for data firms to harvest and repurpose individuals鈥 Facebook information for political and potentially nefarious purposes, just as one U.K. firm stands accused of doing to help Donald Trump鈥檚 election campaign.

It鈥檚 alleged that firm, Cambridge Analytica, covertly harvested data on 50 million users to help Trump鈥檚 presidential campaign build voter profiles for the U.S. election. A Channel 4 sting also captured video of the company鈥檚 top executive, Alexander Nix, suggesting unorthodox methods to help smear an individual鈥檚 political opponents. The company has vehemently denied all of the allegations against it.

Canada鈥檚 former top spy, Dick Fadden, points out that the federal Liberals, Conservatives and NDP have all contracted data firms of their own. Those firms do not face the same allegations as Cambridge Analytica, but their mere existence should be enough to make Canadians think twice about what they share online, Fadden suggests.

鈥淏asically, what they鈥檙e using is a psychological profiling algorithm,鈥 Fadden, the former director of the Canadian Security Intelligence Service, told CTV鈥檚 Your Morning on Tuesday. He explained that these data firms essentially scrape every bit of publicly-available information from social media platforms such as Facebook, then offer that data to political parties for their election campaigns.

鈥淭he key is to give political parties and others access to individually-based information that they can use to advance their purposes,鈥 he said.

On Monday, Canadian Privacy Commissioner Daniel Therrien voiced his concern that political parties are not currently bound by the same data collection laws that apply to commercial companies. 鈥淲e have asked Parliament to consider regulating the collection, use and disclosure of personal information by political parties,鈥 Therrien said in a statement.

He added that a research paper was commissioned 鈥渟ome time ago鈥 to examine the issue.

It鈥檚 unclear what exactly political parties are currently doing with voter data, but Fadden says the smartest thing online users can do is to practice informed consent. That means actually reading the user agreements that most people simply accept without reviewing. It also means being judicious about what you share and interact with on social media, knowing that it might be used to target you.

鈥淢ost people don鈥檛 read these agreements, and they don鈥檛 know exactly what they鈥檙e agreeing to,鈥 he said.

What can be done with my Facebook data?

Your Facebook data is already being used to target you for advertising. For instance, if you鈥檝e been looking at engagement rings, you might start seeing ads for rings or wedding dresses appear on Facebook. And if you鈥檝e been shopping for a vacuum cleaner online, you might start to see Amazon ads for vacuum cleaners in your Facebook feed.

Fadden describes Facebook as a sort of 鈥渧acuum cleaner鈥 that will take in and categorize as much information as its users give it. The more information a user provides, the easier it becomes for advertisers to target that person with things they want.

The same principle can also be applied to a person鈥檚 political beliefs. For instance, Facebook that a group of suspected Russian trolls purchased targeted advertising during the U.S. presidential election, which ultimately spread to 126 million users. The ads were primarily focused on divisive social issues in the United States, and would point users to pages allegedly run, in secret, by Russian agents. Those pages were also dedicated to fanning division through the sharing of fake news, either by smearing a candidate or encouraging politically-active groups to vote for third-party candidates who had no chance of winning.

Robert Mueller, the special counsel appointed to investigate Russian meddling in the U.S. election, last month in connection with those politically-charged Facebook ads. His indictment suggests the Russian-backed organization ran several Facebook pages dedicated to fanning division on both sides of the political spectrum, with names such as 鈥淏lacktivist,鈥 鈥淭rumpsters United,鈥 鈥淪outh United鈥 and 鈥淪ecured Borders.鈥

鈥淭hese groups and pages, which addressed divisive U.S. political and social issues, falsely claimed to be controlled by U.S. activists when, in fact, they were controlled by Defendants,鈥 Mueller wrote in the indictment. Mueller said the groups were targeting their online ads at people in states known to flip-flop between Republican and Democrat.

Facebook adjusted its News Feed in response to the Russian ad scandal last October, but it is again reeling in light of the Cambridge Analytica allegations, with its shares plummeting by approximately $52 billion this week.

U.K. lawmakers have summoned Facebook CEO Mark Zuckerberg to testify on the issue.