Firewalls typically protect a network from malicious incoming traffic. In contrast, the Reverse Firewall monitors outgoing traffic to protect the systems and the network. 
How is a Reverse Firewall useful?
- Monitoring outgoing traffic
A reverse firewall can be used to implement company browsing policies and keep the network “clean”. Network admins can configure the reverse firewall to monitor outgoing traffic and block requests to known malicious sites, pornography, torrent peer-to-peer connections etc.
- Safeguarding against internal threats
A reverse firewall can monitor the network activity within the network – and can track and prevent insiders trying to access confidential data, or attempting malicious activities.
- Preventing the network from turning into a botnet
It also extremely effective in preventing the network from launching DDoS attacks.
Many malicious programs take over systems and networks and create “zombie” armies, and botnets to launch attacks in other systems. Reverse Firewalls can stop outgoing malicious and suspicious traffic and prevent the network from turning into a zombie network and attacking outside websites.
It can thus protect the company from being blacklisted, and also from litigations accusing it of launching DDoS attacks. 
- Doyal, A., Zhan, J., & Yu, H. A. (2012). The Reverse Firewall: Defeating DDOS Attacks Emanating from a Local Area Network. 2012 International Conference on Cyber Security. doi:10.1109/cybersecurity.2012.34
- Firewall protection — in reverse. (n.d.). Retrieved fromhttp://searchsecurity.techtarget.com/news/795719/Firewall-protection-in-reverse