what is Master boot record
MBR is first sector of a data storage device such as HD. It stores information about logical Partition like C:, D: (max 4)
- File type
-Store/end (CHS Format)
-Offset
-Partition Size
-Weather partition is boot-able or not 
- Works with Max 2 TB Drives

Boot Loader - Small bit of code which is used to store boot information.

When an os marks a cluster as a used, but does not allocate any files to them, such clusters are lost clusters.

In windows OS, ScanDisk utility or CheckDisk (windows 10) can identify such lost clusters

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Another way to check the status of your HD is though command prompt in windows:
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Cluster is smallest allocation unit in a hard-drive. Cluster is a set of sectors and tracks. The file system divides the storage on a disk volume into discreet chunks of data for efficient disk usage & performance. This chunks are called cluster. 

To put it in simple terms, you get a sector when you take a bunch of things and divide them. You get a cluster when you take a bunch of things and put them together.

Sector is smallest physical storage unit on a disk platter. Normally holds 512 Bytes and few additional bytes for drive control & error correction.
Data is stored on a disk in a contiguous series (Sharing a common border)
For example: if file size in 700 Bytes, two 512 sectors are allocated to the file.

2015 is already a year of healthcare data breaches and it’s getting worse every day. Earlier this year hackers broke into Antham Database containing around 78 million records. This month, Excellus Blue Cross Blue Shield is the latest health care company to discover a
data breach. Now the big question is why hackers are targeting Health Care Data?

Health care data brings significant value, much more than the financial data. Financial data has a limited lifespan. Prescription & Medical records are permanent. Health care data is also a great resource for identity theft.
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Health care data has a significant resale value in markets too.