Just before the 2013 general election, many Malaysians were alarmed by a viral social media message that claimed 40,000 Bangladeshis had arrived in the country to vote for the ruling Barisan Nasional (BN) coalition.

In some of these posts, there was a photo montage of Malaysia Airlines planes on the tarmac, purported newly arrived Bangladeshis wearing BN T-shirts, and buses waiting to take them to voting centres.

The posts, circulated when tensions were running high in the fiercely fought election, caused some opposition supporters to harass and even carry out citizens' arrests of Malaysian voters - who they thought resembled Bangladeshi nationals - as these people queued to cast their ballots. Only much later did people find out that the news was fake.

That May 2013 poll was touted as Malaysia's first "social media election". That year's political race to influence views online was decisively won by the opposition pact, then known as Pakatan Rakyat.

Today, as Malaysia gears up for the 2018 polls, the social media war will not be so easily won, politicians and experts say.

BN has upped its game, spreading its messaging and resources from traditional state-owned newspapers and television channels to Facebook, Instagram and Twitter.

"With elections nearing, more and more fake news will arise," said Umno Youth vice-chief Khairul Azwan Harun. "I always have this rule that if we do not rebut whatever we are wrongly accused of within three hours, then we have failed."

Umno is the dominant party within BN.

BN is mobilising armies of youthful "cyber troopers" trained to connect with their peers.

Young voters, aged between 21 and 30, make up some 45 per cent of the Malaysian electorate. There were 14.8 million registered voters as of the third quarter of last year. These young people could well decide the outcome of the polls.

Still, as of this month, over four million Malaysians in the 21 to 30 age group have yet to register as voters, Malaysia's Election Commission has revealed.

"It is the youth that will determine who will be the ruling government and making the policies… Due to this, we are going all out on social media," said Mr Dzulkarnain Taib, president and chief executive of Yayasan Media Hebat, a pro-BN charitable foundation under the Prime Minister's Department. "The way you respond can be a game changer."

The government is mulling over a new law to counter fake news, a move the opposition says is aimed at smothering dissent.

Malaysia's de-facto Law Minister Azalina Othman Said on Feb 7 said that the proposed law is necessary because fake news "is a national security issue for the government".

The government last month launched an online news portal called theRakyat.com to canvass for votes and combat "fake news".

And Malaysia's Internet regulator, the Malaysian Communications and Media Commission, in March last year launched sebenarnya.my (truthfully.my, in Malay), an online platform it says will help the public to sift out fake news.

Malaysia's opposition, blocked from the mainstream media and with fewer financial resources, has not been standing still.

In recent years, the opposition has wooed netizens with cheeky videos featuring MPs like Ms Teresa Kok making veiled jibes at Prime Minister Najib Razak's administration.

Voters can expect more of the same, says Parti Keadilan Rakyat (PKR), one of the four parties that make up opposition pact Pakatan Harapan (PH).

"We will definitely exhaust all social media avenues and we will address inaccurate reports when needed," PKR communications director Fahmi Fadzil told The Straits Times. But the emphasis will be on how candidates communicate online, he said.

Age, according to Mr Fahmi, is not a barrier. The opposition's leader and candidate for prime minister, Tun Dr Mahathir Mohamad, is 92. He has more than 362,000 followers on Twitter and over 28 million visitors to his blog.

"If you look at Tun M, he is 92 but somehow, the young can still relate to his posts. It's all about being 'real' that makes it easy for people to warm up and relate to him," Mr Fahmi said.

But judging by the number of Facebook followers and likes, ruling party Umno seems to be in pole position, says Mr Ahmed Kamal Nava, founder of social media analytics firm Politweet. "Umno remains the most popular party with four million followers, contrary to the perception that the opposition is leading in the popularity contest," he told The Straits Times.

PM Najib, 64, has nearly 3.4 million Facebook followers, against Dr Mahathir's 2.5 million followers on Facebook.

And since social media is also about winning hearts, both sides have ramped up the "aww" factor.

One of Dr Mahathir's more popular Facebook posts showed a picture of him and his wife, Tun Siti Hasmah, waiting for the MRT like a young couple, attracting 3,500 likes. Meanwhile Mr Najib gets over 20,000 likes every time he posts a picture of his favourite cat Kiky.

Whether these likes translate into votes is another matter.

The #undirosak (spoilt vote) social media campaign was recently launched by young Malaysian voters disillusioned with the political system. The campaign has reportedly attracted thousands of followers, and online vitriol from both sides of the political divide.

And Politweet believes that both the ruling and opposition parties face an uphill battle to win over young voters no matter how much money they spend on social media.

"What I can say is that interest in politics from the youth has declined, so both sides will have problems reaching out to them," Mr Ahmed Kamal said.