75、Online attacks exploit the fact that sensitive data or encryption keys may be present in the system memory in plaintext when an encrypted volume is mounted.Although super user privileges may be required for launching such attacks, we choose not to trust the administrator account.A general key scavenging attack attempts to intelligently run through the system memory ( ) trying to locate and read encryption keys.Any system that requires the communication of key material between kernel-space and user-space components is vulnerable to a general user-space attack, wherein the attacker tries to capture the key when it is present in the address space of an exploitable user-space process.Daemon masquerading is another online attack on schemes that employ a trusted user-space process for key management.An attacker can replace the trusted daemon with a malicious program or launch a man-in-the middle attack on the kernel-space and user-space channel to gain access to encryption keys.In the page cache attack, an attacker may insert and load a malicious kernel module from the user-space at run-time to traverse the page cache and access file contents.Attacks that require super user privileges may be classified.as hard or easy depending on the level of sophistication and effort required to execute them.Although accessing or modifying specific kernel-space data structures of a running system is difficult even for the administrator, exploiting user space vulnerabilities is clearly easy.In a typical compromise, an attacker may gain super user privileges for a short duration and trivially undertake the above attacks.A distinction between the kernel and user-space from a security perspective is becoming crucial as temporary root attacks become common.(3)、How many methods of online attacks have been mentioned in this paragraph?