DNS Proxywall

Technical Specifications

Latest release	5.67 , 24 Jul 2024 , [Change Log, Previous Releases]
Supported networking	Ethernet, IPv4, IPv6, TCP, UDP, DNS.
Traffic transformation engine	Kernel-mode network driver.
Prerequisites	.NET 4.5.2, up-to-date root certificates (or it will take 2 minutes to start).
Supported OSes	Windows 7*, 8, 8.1, 10, 11, Server 2008 R2*, Server 2012, Server 2012 R2, Server 2016, Server 2019, Server 2022. *For Windows 2008 R2 and 7, required Service Pack 1 + KB3033929 (SHA-2 digital signing). *For Windows 8.1, Server 2012 R2, required KB2995730.
Recommended hardware	CPU 1GHz and above, modern graphics card.
Additional hardware required	none

Overview

Domain Name System (DNS) is how web browsers obtain IP addresses of Internet servers. DNS Proxywall uses a flexible set of rules to restrict access to websites by name patterns and geographical locations. It can also act as a proxy that provides filtering and caching of server names for other computers. To better understand the options when choosing DNS protection, see DNS firewall, DNS proxy, and DNS proxywall. Which one to choose?

DNS Proxywall

DNS Proxywall combines DNS firewalling and proxying in one product. It has a number of features that excite even the most demanding users:

• DNS cache - accelerates web browsing by resolving names instantly.
• Editing of DNS records - lets you specify custom IP addresses for DNS names.
• DNS monitoring - provides real-time visibility of resolved domain names and their countries. On wired networks it can also show which DNS names are resolved by other computers. The log can be viewed and stored for later analysis.
• Activity view filters - keep only important events (blocked, remote resolved, cache resolved, etc.) visible, filtering out noise.
• DNS performance measurement - measures DNS packet round-trips to gauge resolution speed. Multiple metrics help analytical decisions about upstream servers and proxy clients.
• DNS Proxy - allows other computers to use its cache or forwarding capabilities (standard DNS, TCP tunnel, or SSL/TLS tunnel) concurrently.
• Cascading - chains multiple DNS Proxywall servers to aggregate DNS traffic into tunnels and route it flexibly.
• Authentication - secures proxy communication using self-signed certificates and/or IP filtering.
• Load balancing - lets you choose algorithms for distributing DNS requests.
• IP Firewall - blocks direct (non-DNS) IP access, ensuring all traffic resolves through DNS.
• Geo tools - quickly identify territories of server addresses.
• And more...

DNS Monitoring

IMPORTANT: When used on a Virtual Machine, accidental changes by a user to the rules may affect Remote Desktop (RDP) traffic and result in a user lockout. For instructions on how to restore RDP connectivity for a VM, see KB article Restoring Remote Desktop (RDP) connectivity to Azure VM after a user lockout.

DNS Proxywall offers extensive capabilities for DNS traffic monitoring. It monitors the standard DNS traffic between the local computer and remote DNS servers:

• Outgoing DNS traffic originated on the local computer and sent to remote DNS servers
• Incoming and outgoing traffic between DNS clients and DNS Proxywall
• Incoming DNS traffic for local DNS server (if there is a DNS server on the local computer)
• Promiscuous monitoring of traffic between other computers on the local wired network

The activity log shows the status and the action that was taken on the traffic:

• - DNS query was sent the response was not yet received.
• - DNS request was successfully resolved via local DNS cache.
• - DNS request was successfully resolved via internal table of permanent host addresses.
• - DNS request was successfully resolved by DNS server.
• - DNS request was blocked by name pattern rules.
• - DNS request was blocked due to cached response from DNS server contained name resolution refusal.
• - DNS request was blocked due to timeout (exceeded timeout threshold).
• - DNS request was blocked due to geography.
• - DNS request was blocked due to DNS cache only mode and the name was not in the cache.
• - non-DNS (direct address) connectivity was blocked by IP firewall since the IP address does not have matching record within the cache.
• - DNS request was refused by the server (the DNS server was unable to resolve the name).
• - DNS request was picked up in promiscuous monitoring mode and was resolved by DNS server for some other computer.
• - DNS request was picked up in promiscuous monitoring mode and indicates it the failure to resolve the name was communicated between two other computers.

Settings

Upstream DNS Servers

DNS Proxywall can forward packets to other DNS servers. Such DNS servers are called 'upstream' servers since they are located up the stream. The upstream DNS servers can be configured automatically by the program or specified manually.

Add DHCP configured DNS servers option automatically adds to the list standard DNS servers configured during computer connect to the network (during DHCP configuration phase). DHCP configured servers are standard DNS servers that accept incoming requests within DNS protocol over UDP. The upstream servers can be also be added by manually specifying their IP addresses. Only the following types of up-stream servers are currently supported:

• Standard DNS server - a regular server the most often used on the Internet for DNS resolution. Such servers use DNS over UDP protocol.

• Tunnel DNS over TCP proxy - a server uses a proprietary DNS over TCP protocol which wraps DNS traffic into a single TCP tunnel connection to the upstream DNS Proxywall.

• Tunnel DNS over SSL/TLS proxy - a server uses a proprietary protocol which wraps DNS traffic into a single TCP over SSL/TLS encrypted tunnel to the upstream DNS Proxywall.

When forwarding to multiple upstream DNS servers, DNS Proxywall uses load balancing strategy which includes the algorithm for server selection. Currently supported algorithms are:

• Local Only Unchanged -
• First Server Only - all requests are sent to only the first server on the list.
• Round Robin - a request sent to the first server on the list. The next request sent to the next server on the list, and so on.
• Round Robin on timeout - all request are sent to the first server on the list until its first timeout. Then, all requests are sent to the next server on the list, and so on.
• Concurrent - requests are sent to all DNS servers simultaneously. The first received response is taken as a result.

Sometimes forwarded to upstream DNS servers requests are taking to much time. The option Auto block slow requests allows to specify the timeout when to treat the lack of response as a response with refusal(rejection).

When an upstream connection is a tunnel to another DNS Proxywall, the connection is maintained as a keep-alive connection. It does not break after each request. If for any reason the connection breaks, DNS Proxywall would attempt to re-connect after the specified delay. This delay gives the network and the upstream DNS Proxywall some time to resolve the issue.

All statistics on the number of blocked queries, the number of responses from cache and from remote servers are displayed on the Servers tab of the main window. The settings option Show server statistics enables that Servers tab.

When an upstream connection is a TCP or SSL/TLS tunnel to another DNS Proxywall, authentication can be used to prevent unauthorized access. The verification of access is performed using certificates which could be standard certificates issued by certificate authorities or self-signed certificates. Tunnel DNS client authentication option enables such authentication. Once authentication is enabled, the DNS Proxywall provides the same certificate to all upstream servers.

Settings - DNS activity log

Activity log shows all DNS related requests and responses. View size setting specifies the number of records shown within the user interface window. The default value is 1000. User-interface is a performance demanding part of the application. Therefore, the smaller values improve overall performance on servers and workstations with low-end graphics cards.

The activity log can be persistent (stored into a file). This feature can be enabled with DNS log is persistent checkbox. The persistent log is stored (flushed) to disk periodically with the interval specified in Flush to disk period. Activity log files can grow to a very large size. For that reason, they are rotated every day. Each day is stored within the same folder into a log file with a different suffix. The location of the logs can be changed. The logs are produced by the service component of the DNS Proxywall. Therefore they keep growing even when user interface is not running. The default location for the logs is
"C:\Windows\system32\config\systemprofile\AppData\Local\Verigio\DnsProxywallSvc\Logs\".

When DNS Proxywall blocks IP addresses, the number of blocked packets could be astronomical. For that reason, the records with the same IP are aggregated and reported as a single line. The aggregation interval for IP blocking can be set in Blocked non-DNS IP aggregation period. Other attributes related to resolved and blocked records can be added or removed from the view.

• Display round-trip times - shows on the screen the time it took to resolve a DNS record. It is the round-trip from this computer to the DNS server. It is not related to round-trip to the actual server destination stated within the DNS record.

• Round-trip time excludes timeouts - excludes timed-out requests (DNS server did not respond) from round-trip calculation. When DNS servers do not respond for any reason, that  distorts calculations of average values. The exclusion of such abnormalities  allows to calculate more objective picture of the performance.

• Display geo information - shows the flag of the associated with the IP address territory. If the DNS record contains multiple IPs in different territories, only the first territory is shown.

• Activity view filters
  
  displays the filter bar at the top of the log window with checkboxes to filter different types of activity events. These filters affect only the view and not the persistent log.

Settings - DNS cache

DNS Proxywall maintains it own DNS cache. All requests and responses are stored within that cache. When request is resolved via cache rather than via remote DNS server, it saves time on the round-trip packet travel. The total number of cache requests and resolves per DNS server is displayed on Servers tab of the main window. By default, the cache is kept in memory and reset each time the DNS Proxywall service restarts. The option Cache is persistent forces the cache to be saved on disk periodically and loaded upon DNS Proxywall service start.

The cache contains records that come from other (upstream) servers. For hosts that have permanent IP addresses, DNS Proxywall has PermanentHostAddressTable.hostaddr file where permanent IP addresses for server names can be specified. This file is used during IP address resolution before the cache lookup and before sending packets to remote (upstream) servers. Its functionality is similar to hosts file on Windows. The format is similar to the hosts file as well.

Each line could be a blank line, a comment line, or a line with an IP address specification.
[*.]domainname IPAddr1[,IPAddr, ...] [Category] [# comments]

Examples

• The exact case-insensitive match for verigio.com
  verigio.com 192.168.1.1 PermanentHostAddressCategory
  The PermanentHostAddressCategory is a single word tag that describes the host.
• Case-insensitive match to verigio.com and all subdomains
  *.verigio.com 192.168.1.1,192.168.1.2 PermanentHostAddressCategory

The option Confirm cached record delete forces user interface prompt for user confirmation when the user is attempting to manually delete record(s) from the cache. DNS Proxywall supports the use-only-from-cache mode when only previously resolved and cached IP addresses are used while all other attempts to resolve new addresses are automatically rejected. The use-only-from-cache mode is activated by Block network access to not cached IPs option.

Other cache parameters can be set as well.

• Maximum capacity - maximum cache capacity beyond which the older records are replaced by the new ones.

• Cached records expiration - force expiration of cached DNS records. This option helps to keep DNS records up-to-date.

• Cache refused requests - whenever a request is rejected with the status 'no such server', the record can be cached so the subsequent requests to non-existent servers would fail faster.

Settings - Geo DNS

Geo DNS allows to lookup the country of an IP address. It also supports geographical prioritization which is reordering of IP addresses within each DNS record according to specified priority list. The IP addresses belonging to countries at the top of the list will be used for connectivity first. This improves connection performance when connectivity is with hosts located nearby rather than far away. The geographical prioritization can be enabled with Reorder IPs within DNS records by priority. The countries with higher priority should be placed at the top of the Territory priorities list. The dropdown box contains all the territories and networks that can be added to the priority list. NOTE: it sometimes takes up to 1 minute to populate this dropdown box at first.

Geo Definitions Database (GeoDefsDB) update settings

Geo definitions (Geo IP) database contains mappings between geographical territories and IP addresses. This database is stored in a proprietary format. The program comes within the internal (embedded) Geo IP database that is used in absence of later database versions. This embedded database can be set as the primary(active) database by clicking Set Current GeoDefsDB button. Updates to the Geo IP database can be downloaded from our website using this settings page or they can be set to download automatically at predefined time. The initial time at which the download is performed is generated randomly upon the first program start.

The database can be set to automatically download at the specific time of day with a period of several days. The settings for auto download can be found under Auto update GeoDefsDB section.

Geo definitions can also be downloaded manually and saved into a file using Download and Save... button. This helps to manually manage what geo definitions are used. The loading of geo definitions database can be done with Load File... button.

Settings - DNS proxy

DNS Proxywall can act as a DNS server to other computers on the network. The standard DNS server (proxy) functionality is enabled by Standard DNS proxy server setting. When this functionality is enabled, DNS Proxywall is listening for incoming DNS requests on UDP port and sending responses either based on its own cache or based on responses from the upstream DNS servers. The standard DNS server (proxy) functionality supports the widest range of DNS clients from personal computers to mobile phones.

DNS Proxywall also supports tunneled communication. The tunneled communication is a proprietary Verigio protocol and is supported only for traffic between DNS Proxywals. This protocol packages all DNS traffic into a single TCP connection. This feature is commonly used for aggregation of DNS traffic for forwarding to a centralized server(s) via reliable TCP protocol. The tunneled communication listener can be turned on with Tunnel DNS proxy server option. TCP communication can also be encrypted with SSL/TLS protocol on top of the TCP.

When encryption is enabled with Use SSL/TLS, two sides to communication use certificates to encrypt the traffic. Those certificates can be issued by a standard certification authority (CA) or self issued and self signed. When two sides start communication with enabled SSL/TLS, they verify each other's certificates using the SHA-1 checksum. The client knows SHA-1 of the server certificate and the server knows SHA-1 of the client certificate. They both verify SHA-1 of each other, and only then proceed to establishing the connection.

TCP is a connection oriented protocol. Which means that a connection between a server and a client exists until one of the sides decides to disconnect. To prevent multiple clients from consuming server's resource by staying idle, Disconnect idle clients after option forces disconnect of such clients after the specified timeout. When disconnected clients become active again, they would re-connect to DNS Proxywall.

Settings - DNS proxy IP security

Placing a personal DNS proxy on the Internet could be quite risky without the proper security. DNS Proxywall supports verification of clients by IP addresses. Only requests coming from the specified IP addresses and subnets are processed by the program. Other requests are simply ignored.

The options Allow clients from local IPv4 subnets and Allow clients from local IPv6 subnets automatically add IP addresses of all computers on the local network to the list of allowed client IPs. Whether IP is on local or not local network is determined by the network mask(s) configured by DHCP during connect to the network.

Settings - DNS proxy Auth security

The next level in securing the DNS Proxywall in proxy mode is the certificate authentication security. This feature is supported only for tunnel based communication: DNS over TCP, or DNS over SSL/TLS. It allows to ensure authentication of DNS clients with no regard for their IP addresses. In other words, it works independently from IP security.

DNS Proxywall verifies SHA-1 (a.k.a. Thumbprint) hashes of digital certificates provided by clients. Only when certificates match the connection is established. Verification of client certificates is enabled via Verify tunnel DNS client certificates option. The SHA-1 hashes of allowed certificates can be added to the list as hexadecimal text using Add as Text or calculated from the exact client certificate file using Add from File. Hexadecimal SHA-1 text of a certificate can be obtained using either a web browser or just by viewing the special fields of a certificate. The calculation of SHA-1 can be performed on *.p12 (Personal Information Exchange) files. Such files can be encrypted with password as well.

Settings - IP Whitelist

DNS Proxywall rules can block wide range of IP addresses via Geo DNS or via blocking of non-DNS IPs. Sometimes, it is important to guarantee that communication with local network and certain other IP addresses does not get blocked. IP Whitelist allows to exclude IP addresses from such blocking. Whenever DNS Proxywall is managed in the cloud via Remote Desktop, adding your own IP address to the whitelist would prevent locking yourself out by accidental change in rules.

By default, whitelists contain IP addresses that are considered to be special addresses that rarely require any blocking. Whenever changes to the whitelist is needed to be reverted, Reset to Factory Defaults would reset it each whitelist to its original state.

Settings - User Interface

DNS Proxywall has a very dynamic graphical interface. Not all servers have high-end graphics cards that can draw so much graphics efficiently. Therefore, adjusting UI performance is one of the ways to improve overall system performance. DNS Proxywall user interface is needed only for management of the DNS Proxywall service. Once the settings are set, UI can be closed completely. In cases when UI is needed to be on and the overall performance is needed as well, UI performance settings panel allows to adjust various graphical features to better suit the needs.

• Activity log - enables or disables activity logging. It is the equivalent of the setting on the DNS Activity Log tab.
• Upstream server statistics - enables or disables calculation and display of statistics for upstream DNS servers. It is the equivalent of Show server statistics option on the Upstream DNS Servers tab.
• Proxy client statistics - enables or disables calculation and display of statistics for proxy clients. It is the equivalent of Show client statistics option on the DNS Proxy tab.
• Rules statistics - enables or disables calculation and display of statistics for name pattern rules.
• DNS cache statistics - enables or disables calculation and display of s tatistics for each DNS cache record.
• Display Geo information - enables or disables displaying of country flags next to IP addresses.
• Refresh period - refresh period for all statistics. The smaller it is the more overhead it results in.

System tray icon -- allows user interface upon close to be minimized instead to the system tray area of the task bar.

Notes:
* Windows^® is a registered trademark of the Microsoft Corporation.