Computer Security: Q & A

Question 1:

Will you lose data if you keep a magnet near a computer or a hard disk on top of a soundbox?
The hard drive magnets are the rare-earth, permanent, & powerful Neodymium magnets, which forms almost half of the motor or actuator that moves the Read/Write head quickly across the surface of a hard disk platter.  These are really strong magnets. The stronger the magnets, the faster the head can move over the disk in order to reduce the access time. Terabyte-sized drives consist of up to 4 platters that are coated with iron oxide or cobalt, & each have capacities of up to 690GB. This data is stored in small magnetized segments or bits on the disk, which can have two magnetization directions: 0 & 1.


Usually bits are vertically aligned with the disk, & in order to  Read/Write these bits, the hard drive head should move only 10 nanometers over the surface. To read data, the magnetization of bits induces different current strengths in the head due to the massive magnetoresistance effect: 0 & 1. While writing data, the head acts as the electromagnet, which magnetizes the bits with an extremely strong field, because of the short distance. Thus magnetic fields affect data, but in case of hard drives, the disks are so strongly magnetised that only exceptionally strong fields greater than 0.5 Tesla can change the bits. Also it must be remembered that field strength reduces to a fraction after only a few milimeters. So, the powerful Neodymium magnets, when placed near a computer will be too weak to change or erase any data from the hard drive.

Throw Exception:
If a magnet is brought closer to a hard disk, while operating, then the Read/Write head may be deflected, or the head may be pressed against the platter, thus causing errors while writing or physical damage, both leading to data loss.
Question 2:
Will the computer RAM be empty, when its power switches off?


The computer RAM consists of individual memory cells, each called a bit, & again each of these cells consists of a transistor and a capacitor, which either contains an electrical charge (bit value =1) or not (bit value =0). The transistor regulates access on this charge and is thus connected to two electrical lines, viz. the word line & bit line. During Read/Write process, the CPU usually activates the word line first, making the transistor permeable. While writing, the CPU transports information on the bit line, & the charge of the capacitor then aligns with the potential of the bit line, which corresponds to the value 1 or 0.

The capacitor deallocates its charge on the bit line during Write, whereby its potential rises or falls, depending on whether the capacitor is loaded or not. The CPU then interprets this as 1 or 0. As the line is discharged during Read, a fresh writing process begins, which recovers the cell contents, i.e. the Write Back process.

A loaded or charged capacitor saves around 100,000 electrons in each of it at that point. This charge quantity can be cleared very fast by current leakage in the surrounding chip material, when the current supply is cut off. It has been calculated that the internal memory is updated every 15 microseconds, & the memory is not empty in milliseconds, as few cells discharge faster, & some discharge slower. In fact, most of the bits can survive at room temperature for at least 2 seconds, & the charges can survive longer, if the memory chips will be cooled down to lower degrees of temperature, which can be done artificially. Resistance is increased in the semiconductor material of the memory chip at lower temperature, that prevents fast discharging of current leakage.
In the standby mode of a computer, remove the cooled RAM stick & insert it after a few seconds. The computer will wake up from the standby mode. 


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