Firewall Architectures in .NET

Integrate qr-codes in .NET Firewall Architectures
406 12
Draw denso qr bar code with .net
using .net framework topaint qr code iso/iec18004 on asp.net web,windows application
Firewall Architectures
QR Code 2d Barcode barcode library for .net
Using Barcode reader for .NET Control to read, scan read, scan image in .NET applications.
The cost and overhead of the protection mechanism should be relatively low or the system may become too expensive to run. Network administrators deploy and configure a variety of protection mechanisms; hence it is important to have a clear model of what is being protected. The attacks are constantly changing; hence it should be easy to make changes to the configuration of the protection mechanism. It may be necessary to log input and/or output requests for auditing and defence purposes.
Bar Code barcode library on .net
using visual studio .net tointegrate bar code for asp.net web,windows application
Solution
Bar Code barcode library for .net
Using Barcode reader for VS .NET Control to read, scan read, scan image in VS .NET applications.
A PACKET FILTER FIREWALL (405) intercepts all traffic coming and going from a port P and inspects its packets (see the figure below). Those coming from or going to mistrusted addresses are rejected. The mistrusted addresses are determined from a set of rules that implement the security policies of the organization. A client from another network can only access the Local Host if a rule exists authorizing traffic from its address. Specific rules may indicate an address or a range of addresses. Rules may be positive (allow traffic from some address) or negative (block traffic from some address). Most commercial products order these rules for efficiency in checking. Additionally, if a request is not satisfied by any of the explicit rules, then a default rule is applied.
QR-Code barcode library on c#.net
using barcode integration for visual studio .net control to generate, create qrcode image in visual studio .net applications.
request External host
Control qr code jis x 0510 image in .net
using barcode integrated for asp.net control to generate, create qrcode image in asp.net applications.
Packet filter firewall Internet
Control denso qr bar code image with visual basic
using .net toadd qr-codes for asp.net web,windows application
request P Local host
Barcode printing with .net
generate, create bar code none with .net projects
The concept of the packet filter firewall
Barcode 3 Of 9 encoder with .net
use vs .net code 39 extended printing todisplay code39 on .net
Structure
.net Framework Crystal barcode maker on .net
using barcode encoding for .net framework crystal control to generate, create barcode image in .net framework crystal applications.
The figure on page 407 shows an external host requesting access to a local host (a server) through a packet filter firewall. The organization policies are embodied in the objects of class Rule collected by the RuleBase. The RuleBase includes data structures
.net Vs 2010 Crystal pdf417 2d barcode generating on .net
generate, create pdf417 2d barcode none for .net projects
Packet Filter Firewall 407
USD8 barcode library in .net
using visual studio .net todraw code 11 on asp.net web,windows application
and operations to manage rules in a convenient way. The rules in this set are ordered, and can be explicit or default.
Control ecc200 data with .net
to develop datamatrix 2d barcode and gs1 datamatrix barcode data, size, image with .net barcode sdk
ExternalHost address
2D Barcode implementation in .net
using sql reporting service toprint matrix barcode on asp.net web,windows application
1 requestService *
.NET WinForms barcode implementation in .net
using barcode implement for .net windows forms control to generate, create bar code image in .net windows forms applications.
PFFirewall
Produce datamatrix with .net
using report rdlc toassign datamatrix with asp.net web,windows application
requestService1
Pdf417 2d Barcode barcode library with visual c#
using an asp.net form crystal toadd pdf417 on asp.net web,windows application
LocalHost address
Ean 128 Barcode development on visual basic.net
generate, create gs1128 none in visual basic.net projects
1 RuleBase addRule deleteRule modifyRule reorderRule *{ordered} Rule In/out
Control gs1 - 13 size in vb.net
to make ean 13 and ean / ucc - 13 data, size, image with vb barcode sdk
ExplicitRule
Develop pdf417 2d barcode with microsoft word
generate, create pdf417 none on word documents projects
DefaultRule
Class diagram for PACKET FILTER FIREWALL
Dynamics
We describe the dynamic aspects of the PACKET FILTER FIREWALL (405) using a sequence diagram for one of its basic use cases. There is a symmetric use case, filtering an outgoing request, which we omit for briefness. We also omit use cases for adding, removing, or reordering rules, because they are straightforward. See the figure on page 408.
Filtering a Client s Request
Summary. A host in a remote network wants access to a local host to either transfer or retrieve information. The access request is made through the firewall, which according to its set of rules determines whether to accept or deny the request that is, it filters the access request. Actors. A host on an external network (client). Precondition. An existing set of rules to filter the request must be in place in the firewall.
408 12
Firewall Architectures
actor :ExtHost
:PFFirewall
:RuleBase
:Rule
:Service
requestService() requestService() accept checkRule accept requestService()
Sequence diagram for filtering a client s request
Description: 1. An external host requests access to the local host. 2. A firewall filters the request according to a set of ordered rules. If none of the explicit rules in the rule set allows or denies the request, a default rule is used for making a decision. 3. If the request is accepted, the firewall allows access to the local host.
Alternate flow. The request is denied. Postcondition. The firewall has accepted the access of a trustworthy client to the local host.
Implementation
1. Define an organization policy about network access, classifying sites according to our trust in them. 2. Convert this policy into a set of access rules. This can be done manually, which may be complex for large systems. An alternative is using an appropriate commercial product, such as Solsoft [Sol]. 3. Note that the idea of a single point of access is virtual: there may be several physical firewalls deployed at different places. This means that it is necessary to install firewalls at all external boundaries, such as routers or gateways. 4. Write the rules in each firewall. Again, products such as Solsoft and others automatically propagate the rules to each registered firewall.