Linden Lab have blogged about a couple of important issues that could impact your enjoyment of Second Life. One is about account security, which is very important and the other is about potential warnings when you try to install Second Life, which contains helpful knowledge.
The account security blog post; An Important Reminder About Account Security, informs us :
It has come to our attention that some Residents are sending messages – which may appear as popup windows in some viewers – informing other Residents that their accounts have been compromised and encouraging them to contact Support, using a phone number that is not associated with Linden Lab.
These messages are phishing attempts to gain access to your Second Life account. Neither Linden Lab, nor Second Life Customer Support, would attempt to contact you in this manner.
Please make sure you are aware of this issue, the blog post from Linden Lab contains links to support, so it’s well worth taking a look at the post.