Bad news for those who find amusement in email offers touting Viagra and fake Rolexes — and good news for most everybody else: The tidal wave of spam has gone way down. Symantec, the biggest maker of computer-security software, reports that the number of junk emails worldwide dropped precipitously between August and December, 2010, and one reason could be that Rustock, a network of infected computers or "botnet" that accounted for much of the world's spam, has mysteriously shut down almost entirely. One hitch — security pros say the levels could rise again soon. Here's a look at the spam slowdown by the numbers:

200 billion
Number of daily spam messages recorded in August, 2010

50 billion
Number of spam messages recorded in December, 2010

47 or 48 percent
Proportion of global spam that botnet Rustock was responsible for before its mysterious shutdown

0.5 percent
Proportion of spam Rustock is now responsible for

90 percent
Emails that were unsolicited as of May, 2010

46 percent
People who have clicked on a spam message, according to a recent survey

Percentage of people who actually buy a product after clicking on spam, according to The New Scientist

Percentage of tweets that were considered spam in August, 2009 — the spam peak for the site thus far. Spammers have increasingly targeted social networks over the past two years.

The year that spam was first used as a derogatory term for junk email. A marketing manager violated etiquette by sending a mass email promoting a computer product launch through the government and university network that predated the internet. 

Year in which Spam, the precooked canned meat for which junk emails are named, made its debut

Sources: CNN, Toronto Sun, Templetons, Time