One morning in February 1814, Charles de Berenger embarked on what was probably, up until then, the most elaborate known example of securities fraud.

Dressed as an officer loyal to the Bourbons - the French monarchy - de Berenger arrived at the Ship Inn in the British city of Dover with news that Napoleon Bonaparte had been killed by Prussians.

The news travelled to the British admiralty in London by semaphore telegraph, with de Berenger and his co-conspirators stopping by pubs along the way to spread the word for good measure.

Within hours, pamphlets containing stories about Napoleon's purported death were on the street and the price of British bonds soared. That created a seller's market for de Berenger and company who off-loaded their holding of British government bonds, fetching £1.1 million, which is worth £88 million (S$155 million) in today's money, according to an investigation later.

Fake news has been with us for as long as there has been the means to spread the real thing. And it can spread fast. Truth can course-correct just as quickly. The Great Stock Exchange Fraud of 1814 was over the same day it started.

What's different now is how far fake news can spread and the impact it can have, thanks - or no thanks - in large part to social media.

In March, China's Foreign Ministry spokesman Zhao Lijian tweeted to his half a million followers a till-then fringe conspiracy theory that the coronavirus had been brought in by an American serviceman attending a sporting event in Wuhan last October.

The notion found a willing audience among China's citizenry weary of allegations that their country was the cause of the pandemic. Analysts said the conspiracy theory deflected blame from Beijing's early handling of the crisis and paved the way for a narrative of China prevailing against the virus.

The threat of fake news has earned renewed attention with the Covid-19 pandemic and the 2016 US presidential election.

After the election of Mr Donald Trump as president, United States investigations led to the Internet Research Agency in Russia and found the so-called troll farm that had helped manipulate US media coverage by stealing identities of US citizens and spreading incendiary messages about race and religion during the campaign.

In the case of Covid-19, big social media companies, including Facebook, Google-owned YouTube and Twitter, jettisoned their hands-off approach to their content and began removing hoax posts, including false remedies.

In March, Facebook removed a video by Brazil's President Jair Bolsonaro that claimed anti-malarial drug "hydroxychloroquine is working in all places" as a remedy for Covid-19. The US Food and Drug Administration has warned the drug may interfere with heart rhythms in some patients.

Elsewhere, state-backed online disinformation campaigns are accelerating. A report last year from Oxford University showed the number of countries formally conducting online disinformation campaigns surged to 48, from 28 a year earlier.

Social media campaigns often took place during elections and were undertaken by at least one government agency or one political party, the report said. The list includes authoritarian countries such as China and Russia, as well as Western democracies, including the US, United Kingdom, Australia and Germany.

While de Berenger's case was an example of outright securities fraud, the social media campaigns are more sophisticated, with multiple aims including undermining journalism, the report said.

"In many countries around the world, divisive social media campaigns have heightened ethnic tensions, revived nationalistic movements, intensified political conflict, and even resulted in political crises - while simultaneously weakening public trust in journalism, democratic institutions and electoral outcomes," the report said.

A poll conducted in April by Pew Research found that only 48 per cent of respondents had either a "fair amount" or a "great deal" of confidence that journalists will act in the public interest. This was down from 55 per cent two years earlier.

Disinformation can also be a corporate strategy. In February, Facebook said Vietnamese telco Viettel was linked to fake accounts criticising rivals.

All this is salient because social media is increasingly a key source of news. In 2012, only 27 per cent of respondents in a US survey conducted by Oxford's Reuters Institute said they got their news from social media. Within five years that percentage ballooned to 51 per cent.

There has been a flurry of legislation passed in recent years to counter disinformation online, prompting criticism that the moves amount to official censorship.

Last October, Singapore passed legislation giving ministers the power to require social media companies to post corrections to what they deem as false or misleading content. Repeat offenders will be blocked. Thailand and Indonesia have passed similar laws.

Innovative initiatives aimed at encouraging the spread of accurate Covid-19 information have also emerged. The British government is shelling out £500,000 for social media influencers overseas, including to KlikDokter in Indonesia, which has more than four million followers on Facebook.

With a billion hours of video being watched every day on YouTube, finding and removing disinformation is a big task.

But social media companies have vast resources at their disposal. Facebook posted net income of US$4.9 billion (S$6.8 billion) during the first three months of the year.

Social media companies also argue they are not publishers like newspapers and cannot be held responsible for what is spread on their platforms. But critics say moves to remove Covid-19 hoaxes suggest the companies acknowledge some responsibility for the content on their platforms.

The social media giants may also wish to avoid seeming as if they are taking sides. When Twitter flagged a post by President Trump - which claimed mail-in ballots are unsafe - as inaccurate, he threatened to close the platform.

More than 200 years since de Berenger posed as a Bourbon officer as part of an elaborate ruse to defraud debt markets, fake news is still with us. The problem is that there is much more of it and there's more at stake.

With their reach, social media platforms are increasingly seen as utilities in need of regulation. Carrots and sticks - criminalisation and incentives - are part of the solution. But so, too, must be a less credulous consumer base. One would think we would have learnt by now.