1) This is rootkit driver which come packaged in malware. Main reason of this malware is to destroy AV which cannot be finished from user mode usually. When Rootkit.Indag.A gets loaded on PC then it registers as device in name \\Device\\GanDiao. Now user mode application able to utilize this driver to destroy any process.

2) When PC gets infected by viruses then those virus send data to attacker about PC. If PC is not protected by strong password then anybody can access user account. You can make strong password by making it of about 8 characters combining letters, numbers, and symbols.