People want Google+ invites badly.

Google plus invite, please? begged a desperate netizen on Twitter (never mind that Google has temporarily stopped accepting new users).

So when people receive an invite for Google+, even if it's from someone they don't know, some just can't resist.

Cyber security firm Sophos exposed a Google+ invite scam that sends out invites that look like the real thing, except the link takes the tricked users to a pharmacy Web site that sells Viagra. The site even features a special July 4th sale.

Taking advantage of overwhelming demand and offering something too good to refuse is a tried and true technique criminals use online.

For example, back when Gmail invites were a hot commodity, criminals sent out a bogus email to Gmail users to inform them that they have more Gmail invites. To activate these new invites, all they have to do is type in their username and password in a submission form.

Since Gmail invites were a big deal and even worth money (just like how Google+ invites are currently being sold on eBay), some Gmail users couldn't resist and fell for the phishing scam.

Another example is criminals offering people to be iPad beta testers via Facebook and Twitter. As a part of the too-good-to-be-true deal, the 'testers' were to receive the iPads early and keep them free of charge.

All they have to do is submit their personal information to a quiz website (supposedly to confirm that the beta testers were human beings). If an invalid phone number was entered, the submission will be rejected.

Once a valid phone number is entered, however, that phone number will signed up to a premium phone service that cost $10 per week, according to Sophos.

The lesson from all of this is the following: whether it's Google+ invites, free iPads, or Facebook's awesome thing next week, don't fall for something that's too good to be true and from a source that you haven't verified.

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