Rowhammer: How Repeated RAM Access Can Flip Bits Without Any Permission Breach

Rowhammer is a hardware-level attack that exploits a physical vulnerability in DRAM memory chips to corrupt data without ever violating software permissions. Each bit in DRAM is stored in a capacitor-transistor cell arranged in dense rows, and accessing a row generates electrical disturbances that can affect neighboring rows. When an attacker repeatedly activates the same memory row hundreds of thousands of times per second, the cumulative interference can cause a bit in an adjacent protected row to flip its value. This occurs because the standard DRAM refresh mechanism is not designed to compensate for such abnormally high activation rates. A more aggressive variant called double-sided hammering targets rows on both sides of the victim row, increasing the likelihood of inducing a bit flip.