A buffer overflow (or buffer overrun) occurs when the volume of data exceeds the storage capacity of the memory buffer. As a result, the program attempting to write the data to the buffer overwrites adjacent memory locations.
Buffer overflow is a vulnerability in low level codes of C and C++. An attacker can cause the program to crash, make data corrupt, steal some private information or run his/her own code. It basically means to access any buffer outside of it's alloted memory space. This happens quite frequently in the case of arrays.

Security Intelligence Sources ... Custom Block lists or feeds (or objects or groups) Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy. Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/623/configuration/guide/fpmc-configguide-v623/security_intelligence_blacklisting.html
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Custom Block lists or feeds (or objects or groups)
Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy.
Security Intelligence Sources ... Custom Block lists or feeds (or objects or groups) Block specific IP addresses, URLs, or domain names using a manually-created list or feed (for IP addresses, you can also use network objects or groups.) For example, if you become aware of malicious sites or addresses that are not yet blocked by a feed, add these sites to a custom Security Intelligence list and add this custom list to the Block list in the Security Intelligence tab of your access control policy. Reference: https://www.cisco.com/c/en/us/td/docs/security/firepower/623/configuration/guide/fpmc-configguide-v623/security_intelligence_blacklisting.html

The command "crypto isakmp identity address 172.19.20.24" is not valid. We can only use "crypto isakmp identity {address | hostname}. The following example uses preshared keys at two peers and sets both their ISAKMP identities to the IP address. At the local peer (at 10.0.0.1) the ISAKMP identity is set and the preshared key is specified: crypto isakmp identity address crypto isakmp key sharedkeystring address 192.168.1.33 At the remote peer (at 192.168.1.33) the ISAKMP identity is set and the same preshared key is specified: crypto isakmp identity address crypto isakmp key sharedkeystring address 10.0.0.1 Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/security/a1/sec-a1-cr-book/sec-crc4.html#wp3880782430 The command "crypto enrollment peer address" is not valid either. The command "crypto ca identity ..." is only used to declare a trusted CA for the router and puts you in the caidentity configuration mode. Also it should be followed by a name, not an IP address. For example: "crypto ca identity CA-Server" -> Answer A is not correct. Only answer B is the best choice left.
identity {address | hostname}. The following example uses preshared keys at two peers and sets both their ISAKMP identities to the IP address.
At the local peer (at 10.0.0.1) the ISAKMP identity is set and the preshared key is specified:
crypto isakmp identity address
crypto isakmp key sharedkeystring address 192.168.1.33
At the remote peer (at 192.168.1.33) the ISAKMP identity is set and the same preshared key is specified:
crypto isakmp identity address
crypto isakmp key sharedkeystring address 10.0.0.1
Reference:
The command "crypto enrollment peer address" is not valid either.
The command "crypto ca identity ..." is only used to declare a trusted CA for the router and puts you in the caidentity configuration mode. Also it should be followed by a name, not an IP address. For example: "crypto ca identity CA-Server" -> Answer A is not correct.
The command "crypto isakmp identity address 172.19.20.24" is not valid. We can only use "crypto isakmp identity {address | hostname}. The following example uses preshared keys at two peers and sets both their ISAKMP identities to the IP address. At the local peer (at 10.0.0.1) the ISAKMP identity is set and the preshared key is specified: crypto isakmp identity address crypto isakmp key sharedkeystring address 192.168.1.33 At the remote peer (at 192.168.1.33) the ISAKMP identity is set and the same preshared key is specified: crypto isakmp identity address crypto isakmp key sharedkeystring address 10.0.0.1 Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/security/a1/sec-a1-cr-book/sec-crc4.html#wp3880782430 The command "crypto enrollment peer address" is not valid either. The command "crypto ca identity ..." is only used to declare a trusted CA for the router and puts you in the caidentity configuration mode. Also it should be followed by a name, not an IP address. For example: "crypto ca identity CA-Server" -> Answer A is not correct. Only answer B is the best choice left.