The Great Firewall was formerly operated by the SIIO, as part of the Golden Shield Project. Since 2013, the firewall is technically operated by the Cyberspace Administration of China (CAC), which is the entity in charge of translating the Chinese Communist Party's doctrine and policy into technical specifications.
As mentioned in the "one country, two systems" principle, China's special administrative regions (SARs) such as Hong Kong and Macau are not affected by the firewall, as SARs have their own governmental and legal systems and therefore enjoy a higher degree of autonomy. Nevertheless, the U.S. State Department has reported that the central government authorities have closely monitored Internet use in these regions, and Hong Kong's National Security Law has been used to block websites documenting anti-government protests.
The term Great Firewall of China is a combination of the word firewall with the Great Wall of China. The phrase "Great Firewall of China" was first used in print by Australian sinologist Geremie Barmé in 1997.
One function of the Chinese firewall is to selectively prevent content from being accessed. It is mostly made of Cisco, Huawei, and Semptian hardware. Not all sensitive content gets blocked; in 2007, scholar Jedidiah R. Crandall and others argued that the main purpose is not to block 100%, but rather to flag and to warn, in order to encourage self-censorship. An illustrative but incomplete list of tactics includes:
Contrary to popular belief, foreign DNS resolvers such as Google Public DNS IP address 18.104.22.168 are reported to work correctly inside the country; however, these DNS servers are also subject to hijacking as their connections aren't encrypted: DNS queries do reach the DNS server, but if the request matches a banned keyword, the firewall will inject a fake DNS reply before the legitimate DNS reply arrives.
In addition to previously discussed techniques, the CAC is also using active probing in order to identify and block network services that would help escaping the firewall. Multiple services such as Tor or VPN providers reported receiving unsolicited TCP/IP connections shortly after legitimate use, for the purported purpose of network enumeration of services, in particular TLS/SSL and Tor services, with the aim of facilitating IP blocking. For example, shortly after a VPN request is issued by a legitimate Chinese VPN client and passes outbound though the Great Firewall to a hidden VPN IP, the Great Firewall may detect the activity and issue its own active probe to verify the nature of the previously unknown VPN IP and, if the probe confirms the IP is part of a blacklisted VPN, blacklist the IP. This attack can be circumvented with the Obfs4 protocol, which relies on an out-of-band shared secret.
The Cybersecurity Law behind the firewall being targeted at helping increase internet user privacy, increased protections on personal data, and making companies more responsible for monitoring bad actors, in hopes to make a safer place on the internet for Chinese citizens. Despite this, there have been growing criticisms that the actions of the Chinese government have only hurt Chinese free speech, due to increased censorship, and lack of non-sanctioned sources of information, such as Wikipedia and many English news sources. This has resulted in reports of some cases of legal persecution of those charged with spreading this information.
While the Great Firewall has had an impact on Chinese citizens' ability to use the internet to find information about sensitive topics about the Communist Party, it has not completely stopped them from doing so. The firewall itself has caused much frustration amongst both individuals and internationally operating companies in China, many of whom have turned to VPNs, speaking in codes, and other methods to retain their access to the international internet.
Because the Great Firewall blocks destination IP addresses and domain names and inspects the data being sent or received, a basic censorship circumvention strategy is to use proxy nodes and encrypt the data. Bypassing the firewall is known as fanqiang (翻墙, "climb over the wall"), and most circumvention tools combine these two mechanisms:
While mapping out firewall rules can be valuable, bypassingrules is often the primary goal. Nmap implements many techniques fordoing this, though most are only effective against poorly configurednetworks. Unfortunately, those are common. Individual techniqueseach have a low probability of success, so try as many different methodsas possible. The attacker need only find one misconfiguration to succeed, whilethe network defenders must close every hole.
Many other scan types are worth trying, since the targetfirewall rules and target host type determine which techniques willwork. Some particularly valuable scan types areFIN,Maimon,Window,SYN/FIN, andNULL scans.These are all described in Chapter 5, Port Scanning Techniques and Algorithms.
One surprisingly common misconfiguration is to trust trafficbased only on the source port number. It is easy to understand howthis comes about. An administrator will set up a shiny new firewall,only to be flooded with complains from ungrateful users whoseapplications stopped working. In particular, DNS may be brokenbecause the UDP DNS replies from external servers can no longer enterthe network. FTP is another common example. In active FTP transfers,the remote server tries to establish a connection back to the clientto transfer the requested file.
Secure solutions to these problems exist, often in the form ofapplication-level proxies or protocol-parsing firewall modules.Unfortunately there are also easier, insecure solutions. Noting thatDNS replies come from port 53 and active FTP from port 20, many administratorshave fallen into the trap of simply allowing incoming traffic fromthose ports. They often assume that no attacker would notice andexploit such firewall holes. In other cases, administrators consider this ashort-term stop-gap measure until they can implement a more securesolution. Then they forget the security upgrade.
Now that many individual techniques forbypassing firewall rules have been covered, it is time to put them together in a real-life penetration testing scenario. Itall started witha postto the SecurityFocus pen-test list from security proMichael Cain.He and coworkerDemetris Papapetrouwere penetration testing theinternal network of a large corporation and had just bypassed firewall rules meant toprevent one VLAN from accessing another. I was pleased to read thatthey performed this feat using Nmap, and I wrote them for the wholestory. It is both instructional and inspirational in that itdemonstrates the value of perseverance and trying every technique youknow, even after the most common exploits fail. Don't let thatfirewall beat you!
If a filter is causing the problem, it could be a simplestateless firewall as is commonly available on routers and switches.As discussed in previous sections, these sometimes allow TCP ACKpackets through unmolested. Demetris repeats the scan, butspecifies -sA for an ACK scan ratherthan -sS. Any unfiltered portsfound by the scan would suggest that the ACK packets made it throughand elicited a TCP RST response from the target host. Unfortunately,the results were all filtered in this case, just aswith the SYN scan.
The netsh advfirewall firewall command-line context is available in Windows Server 2012 R2. This context provides the functionality for controlling Windows Firewall behavior that was provided by the netsh firewall firewall context.
The netsh firewall command-line context might be deprecated in a future version of the Windows operating system. We recommend that you use the netsh advfirewall firewall context to control firewall behavior.
Some examples of frequently used commands are provided in the following tables. You can use these examples to help you migrate from the older netsh firewall context to the new netsh advfirewall firewall context.
Windows Firewall is a stable, host-based firewall for incoming traffic. Unlike router-based firewalls you deploy at the boundary of a private network and the Internet, Windows Firewall acts as a firewall for host-based traffic you assign to an IP address.
"be on the pc that is physically connected to the "admin" ethernet slot on the sophos" How do you set this shit in Sophos? Got tha firewall in my company, but I can connect on every pc to my firewall.
A rainbow table attack is one wherein an attacker uses a rainbow hash table to crack the passwords stored in a database. A rainbow table is a precomputed lookup table used to reverse cryptographic hash functions. The table can be used to recover a function up to a certain length comprising a limited set of characters.
In the example above, the module was able to identify two valid user accounts (root and blank), retrieve the hmac-sha1 password hashes for these accounts, and automatically crack them using an internal wordlist. If a database is connected, Metasploit will automatically store the hashed and clear-text version of these credentials for future use. If a user's password is not found in the local dictionary of common passwords, an external password cracking program can be employed to quickly brute force possible options. The example below demonstrates how to write out John the Ripper and Hashcat compatible files.
Thanks to atom, the main developer of Hashcat, version 0.46 or above now supports cracking RAKP hashes. It is worth noting that atom added support for RAKP within 2 hours of receiving the feature request! In the example below, we use hashcat with RAKP mode (7300) to brute force all four-character passwords within a few seconds.
As far as implementation goes, the easiest way to do it would probably be from the web server itself (for example, using apache .htaccess files). If you decide to do it from the firewall, you will have to find a way for the firewall to know that someone is requesting the login form and not some other page on the website, assuming that there are other pages besides the login form on this server. Since you are using HTTPS, you'd probably have to terminate SSL at the firewall. 2b1af7f3a8