It’s no secret that corporate inboxes are stuffed with e-mail messages that are – let’s be kind here – unneeded or unwanted. And the latest report from anti-virus software maker Symantec Corporation confirms this in spades.

The report, covering April activity, claims that unsolicited e-mail makes up nearly 91% of messages on corporate networks. And it turns out this is nothing unusual, as earlier surveys have shown that spam makes up anywhere from 80% to 95% of all e-mail volume on the Internet.

So when you look at your own inbox, you might be pleased if your spam volume isn’t that high. And probably it isn’t, because corporate spam filters are blocking a big volume of e-messages before they ever hit your own inbox.

So where is all of this spam coming from? Symantec reports that nearly 60% of it comes from botnets, which are networks of hacked computers that can do all sorts of mischief – not only e-mailing spam, but also swiping financial information or launching cyber attacks. The “worst of the worst” are donbot spammers, which are computers that are available for rent on the black market. According to Symantec, those represent more than 18% of all spam e-mail volume.

But of course, nothing stays the same for long in the cyber environment. A new, even more alarming trend is being noted with an increase of non bot-driven spam. In those cases, spammers are renting legitimate network services (usually located offshore) and blasting huge amounts of spam at large individual Internet service providers. The objective is to push as many messages as possible onto the network before the ISP’s filtering software is able to detect it.

How much of this is going on? Hundreds of thousands of messages each day, and getting greater all the time.

And if that wasn’t enough, just like flies at a Fourth of July picnic, spammers have now discovered social networks, taking over an alarming number of Facebook and Twitter accounts and phishing for user passwords. These swiped passwords are then used to spam the friends of victims with obnoxious unwanted promotional mail about various products let’s just refer to euphemistically as “personal” or “intimate.” Experts say these types of attacks are particularly effective because they can’t be filtered at a corporate firewall level, and because any such message looks like it’s been sent by a friend of the recipient.

So if you’re on any of these social networking platforms, despite their apparent safety, the watchword should still be: “Caution.”