By Daily Mail Reporter
Last updated at 5:57 AM on 7th January 2011

It might not have seemed obvious as you cleared out your inbox, but the number of junk emails sent worldwide plunged in the final months of the year.

Around 200 billion spam emails were being sent everyday in August last year but by December, that figure had dropped to around 50 billion.

Three of the largest culprits for the irritating missives reduced their output over Christmas but experts have warned the lull is probably only temporary.

Spam slump: Junk email traffic fell dramatically in the final months of 2010

Spam slump: Junk email traffic fell dramatically in the final months of 2010

According to security firm Symantec, spam traffic produced by the Rustock botnet was down to less than 0.5 per cent of worldwide junk in December.

Yet at its peak, the spam network was responsible for almost half - 47 to 48 per cent - of all spam sent globally, according to a BBC report.

Two other bots - Lethic and Xarvester - have been largely inactive since December 28 and 31, respectively.

While the drop might hint at a future without junk emails about sex enhancements and get-rich-quick schemes, analysts have said numbers are almost certain to pick up.

'Whilst this is an excellent gift over the holiday season for anyone who regularly uses email, we would not expect the level of spam to stay this low for long,' said Symantec malware data analyst Mathew Nisbet in a blog post.

'As we saw after the closure of McColo in 2008, and following further takedown attempts in subsequent years, botnets rarely stay quiet for very long.

'Even if these three botnets don't come back soon, we would expect other botnets, even new ones, to pick up where they have left off - very soon.'

Carl Leonard, a researcher at security firm Websense, added: 'If a campaign is not getting the returns they want they can stop, regroup and try something else.'

It is believed spammers may be turning to social networking sites like Facebook and Twitter to distribute junk messages.