One of the most impactful types of attacks include Man-in-the-Middle, identity spoofing, virus/worms/Trojans, and sniffers.

When it comes to Man-in-the-Middle attacks, it could be a malicious interception of any sort of network communications, including both internal and external networks. Since communication between two people is intercepted, the actual parties involved might not be getting the real message intended for them. Some of the measures that can be taken to mitigate MITM attacks is by encrypting your data before sending it over to someone. The security team should also ensure that only valid certificates and certification authorities are used with enterprise applications. TLS/SSL Setups also need to be verified and older algorithms or weak for encryption and authentication — such as NULL, RC4, 3DES, MD5, and SHA1 — along with older versions of protocols, such as SSL and TLS versions prior to v1.2 should be disabled. Adding static ARP entries into the cache is one method of mitigating ARP cache poisoning attacks and prevent MITM attacks. 

Identity Spoofing is the act of assuming the identity of some other entity and then using that identity to accomplish a goal. A form of this attack can be used to hijack credentials from legitimate users. Some of the ways to mitigate this is user education. If users are aware of the latest techniques, they are less likely to fall prey to it. Users can use two or multi-factor authentication, install anti-spoofing detection software, and do not click on unknown email links or attachments.

Virus/worms/Trojans can lead to compromising the entire system. To avoid this, users should have the latest and updated antivirus software installed. They should keep their OS current as well.  

Sniffers can be used to collect plaintext sensitive material such as passwords. Link layer encryption and end-to-end encryption are good precautions to take against sniffers. VPNs can also be used to mitigate this threat.