Since Web2.0 (1999) the internet has been used for many way and has introduced many threats, these range from security to health threats. There are 4 main types of threats that can hack your computer and get your details (ranging from your social network password, to your bank details).
Virus
Viruses self propagate (reproduce) to infect other computers, it is a type of Malware that can be linked with other types of Malware (e.g. Trojans sending themselves to your friends, or other computers via a LAN).
Malware
Malware stands for Malicious Software, there are different forms of Malware, they mainly are embedded in software installed or in images (which is really an executable file) and fetch your personal information (passwords and account information) or take up hard drive space & CPU for illegal activity's.
Also, Norton Antivirus, a piece of Software you get a free trail for can be considered a type of Malware, after the 1,3 or 6 month trail they will send notifications on a regular basis to get you to upgrade to a Premium account (which you have to pay for). It would come under the definition of Malware because: It's free (to begin with) then it keeps sending you notifications on a regular basis.
Phishing
Phishes look like they are from a official, but aren't, they hack your information easily because you give them your information, they normally use Spoof sites to Phish.
Spam
It is one threat that nearly everyone is aware of, it is unwanted emails, that will offer you free services, also they may types of Malware.
Health
Also since the introduction of IT it has introduced many health issues, these range from; neck, eye, hand, and generally over time effects. The way you sit when using a computer might not be good for you health, leaning forward and bending your neck, and sitting close will effect your vision can all effect your health. Then there's RSI (repetitive strain injury) which is a pain when you do an activity repetitively without rest, it might not have a long term effect but it still effects your health.
There are also people who are Electrosensitive, this is when Wi-Fi and cellular signals (which is basically radiation) causes a range of symptoms; headaches, tinnitus, chest pains, difficulty sleeping, loss of concentration, effecting memory, change in behavior and a lot more.
Ensure safety and security
First of all do never give your password to anyone, even if they do sound legitimate, also do not disclose any personal information out to the public (for example where you live), since when you post it, it is public and anyone could see it.
Some companies/sites create cookies, these can track were you've been and target you with adds, although this is not really a security risk it is worth mentioning. To remove these you can simply go into your browsers settings and delete them (on Chrome go to: Settings, Show advanced settings..., Privacy, Clear browser data, Delete cookies and other site and plug-in data, then clear).
The best thing to do is; install an antivirus (although windows comes with antivirus pre-installed), check everything sent to you (thought the antivirus, and with the aid of a Firewall), when using public Wi-Fi do not do anything private (entering passwords), when sending private data (bank account details) make sure it has HTTPS (or a padlock next to the address) and check the address of the site you are visiting (to make sure it's legitimate, and not a Phish).
As it comes to separate private blogs from public blogs, there are setting to protect security and privacy, for example if you go to Bloggers settings you will see this:
You can select who can post to your blog, and who can view your posts.
