You have discovered that there are entries in your network's domain name server that point legitimate domains to unknown and potentially harmful IP addresses. What best describes this type of attack?

DNS poisoning occurs when false DNS information is inserted into legitimate DNS servers, resulting in traffic being redirected to unwanted or malicious sites. A backdoor provides access to the system by circumventing normal authentication. An APT is an advanced persistent threat. A Trojan horse ties a malicious program to a legitimate program.