- Most firewalls have two ports, one connected to the intranet and the other to the outside world. - WWW, FTP or any other application) server? On either side of the firewall the server is exposed to attacks, either from insiders or from outsiders.. - If an attack is detected or an alarm is triggered, it collects data on the attackers, their source, and the route they are using to attack the system. - They can also be programmed to automatically print these results, e-mail them to the designated person, or initiate a real-time response via SNAP or a pager.. - Some firewalls will even send out a global distress call to all its peers (from the same manufacturer) and inform them of the origin of the attack. - Basically, an application layer firewall acts as an ambassador for a LAN or intranet connected to the Internet. - Proxies tend to perform elaborate logging and auditing of all the network traffic intended to pass between the LAN and the outside world, and can cache (store) information such as web pages so that the client accesses it internally rather than directly from the Web.. - A proxy server or application layer firewall will be the only Internet connected machine on the LAN. - The rest of the machines on the LAN have to connect to the Internet via the proxy server, and for them Internet connectivity is just simulated.. - Because no other machines on the network are connected to the Internet, a valid IP address is not needed for every machine. - Since all hosts on the network have to access the outside world via the proxy, any machine on the network that requires Internet access usually needs to be configured for the proxy. - A proxy server hardly ever functions at a level completely transparent to the users. - Furthermore, a proxy has to provide all the services that a user on the LAN uses, which means that there is a lot of server type software running for each request. - Generally speaking this is one of the easiest firewalls to configure or use.. - Intrusion detection is a new technology that enables network and security administrators to detect patterns of misuse within the context of their network traffic. - IDS is a growing field and there are several excellent intrusion detection systems available today, not just traffic monitoring devices.. - There are two ways that intrusion detection is implemented in the industry today: host- based systems and network-based systems.. - Host-based intrusion detection systems use information from the operating system audit records to watch all operations occurring on the host on which the intrusion detection software has been installed. - This analysis of the audit trail, however, imposes potentially significant overhead requirements on the system because of the increased amount of processing power required by the intrusion detection software. - Depending on the size of the audit trail and the processing power of the system, the review of audit data could result in the loss of a real-time analysis capability.. - Network-based intrusion detection, on the other hand, is performed by dedicated devices (probes) that are attached to the network at several points and passively monitor network activity for indications of attacks. - Network monitoring offers several advantages over host-based intrusion detection systems. - Because intrusions might occur at many possible points over a network, this technique is an excellent method of detecting attacks which may be missed by host-based intrusion detection mechanisms.. - Independence from audit trails also frees network-monitoring systems from possessing an inherent weakness caused by the vulnerability of the audit trail to attack. - Intruder actions, which interfere with audit functions or which modify audit data can lead to the prevention of intrusion detection or the inability to identify the nature of an attack.. - Another significant advantage of detecting intrusions without relying on audit data is the improvement of system performance, which results from the removal of the overhead imposed by the analysis of audit trails. - Certification is the process of proving that the performance of a particular piece of equipment conforms to the laid-down policies and specifications. - Access to the Web. - One of the biggest weaknesses in security practice is the large number of cases in which a formal vulnerability analysis finds a hole that simply cannot be fixed. - In the case of the firewall, the policy should list:. - The necessary controls on the service, either technical or behavioral. - The security impact of the service. - Many firewalls expose details of TCP/IP application behavior to the end user.. - Unfortunately, there have been cases where individuals bought firewalls and took advantage of the firewall’s easy ‘point and click’ interface, believing they were safe because they had a firewall. - When starting to certify components of a system, one will need to research existing holes in the version of the components to be deployed. - Depending on the size/complexity of the security system in question, one could be looking at anything between a day’s work and several weeks.. - In the process of developing a corporate security consciousness, one will, amongst other things, have to:. - Generate credibility and visibility of the information security effort by visibly driving the process from a top management level. - The topics covered in the security policy document should, for example, include:. - In the process of implementing security policies, one need not re-invent the wheel.. - There are several security advisory services available to the systems administrator. - The CERT (Computer Emergency Response Team) co-ordination center is based at the Carnegie Mellon Software Engineering Institute and offers a security advisory service on the Internet. - The latter include topics such as:. - These are the people whose day-to-day activities include installation, configuration and maintenance of the computers and networks.. - Indeed, Julius Caesar is credited with creating one of the earliest cryptographic systems to send military messages to his generals.. - Consequently, the term key management refers to the secure administration of keys to provide them to users where and when they are required.. - However, there always remains the difficult problem of how to securely transfer the key to the recipients of a message so that they can decrypt the message.. - A major advance in cryptography occurred with the invention of public-key cryptography. - The primary feature of public-key cryptography is that it removes the need to use the same key for encryption and decryption. - With public-key cryptography, keys come in pairs of matched ‘public’ and ‘private’ keys. - The public portion of the key pair can be distributed in a public manner without compromising the private portion, which must be kept secret by its owner. - Encryption done with the public key can only be undone with the corresponding private key.. - Prior to the invention of public-key cryptography, it was essentially impossible to provide key management for large-scale networks. - The invention of public-key cryptography was of central importance to the field of cryptography and provided answers to many key management problems for large-scale networks. - For all its benefits, however, public-key cryptography did not provide a comprehensive solution to the key management problem.. - Indeed, the possibilities brought forth by public-key cryptography heightened the need for sophisticated key management systems to answer questions such as the following:. - The encryption of a file once for a number of different people using public-key cryptography. - The certainty that a public key apparently originated from a specific individual is genuine and has not been forged by an imposter. - The assurance that a public key is still trustworthy. - The next section provides an introduction to the mechanics of encryption and digital signatures.. - Remember that both the client and the bank are in possession of matching private key/public key sets. - The private keys need to be guarded closely, but the public keys can be safely transmitted across the Internet since all it can do is unlock a message locked (encrypted) with its matching private key. - The simplest electronic version of the cheque can be a text file, created with a word processor, asking a bank to pay someone a specific sum. - Since someone else could create a similar counterfeit file, the bank needs to authenticate that it was actually you who created the file.. - Establishing the source of a message so that the sender cannot later claim that they did not send the message. - Since the sender could deny creating the file, the bank needs non- repudiation.. - Since someone could alter the file, both the sender and the bank need data integrity.. - The first step is to ‘sign’ the cheque with a digital signature.. - The process of digitally signing starts by taking a mathematical summary (called a hash code) of the cheque. - This hash code is a uniquely identifying digital fingerprint of the cheque. - If even a single bit of the cheque changes, the hash code will dramatically change.. - The next step in creating a digital signature is to sign the hash code with the sender’s private key. - This signed hash code is then appended to the cheque.. - How is this a signature? Well, the recipient (in this case the bank) can verify the hash code sent to it, using the sender’s public key. - At the same time, a new hash code can be created from the received check and compared with the original signed hash code. - If the hash codes match, then the bank has verified that the cheque has not been altered. - The bank also knows that only the genuine originator could have sent the cheque because only he has the private key that signed the original hash code.. - This is often referred to as a symmetric key system because the same key is used at both ends of the process.. - As the cheque is sent over the network, it is unreadable without the key, and hence cannot be intercepted. - The next challenge is to securely deliver the symmetric key to the bank.. - Public-key encryption is used to solve the problem of delivering the symmetric encryption key to the bank in a secure manner. - To do so, the sender would encrypt the symmetric key using the bank’s public key. - Since only the bank has the corresponding private key, only the bank will be able to recover the symmetric key and decrypt the cheque.. - Why use this combination of public-key and symmetric cryptography? The reason is simple. - Public-key cryptography is relatively slow and is only suitable for encrypting small amounts of information – such as symmetric keys. - Symmetric cryptography is much faster and is suitable for encrypting large amounts of information such as files.. - The more transparent the system is, the easier it is for end-users to use – and the more likely they are to use it. - The most convenient way to secure communications on the Internet is to employ public-key cryptography techniques. - verify the public keys of the party with whom he or she wishes to communicate. - This is where a public-key infrastructure comes in.. - A successful public-key infrastructure needs to perform the following:. - Deploying a successful public-key infrastructure requires looking beyond technology. - As a result, the quality, integrity, and trustworthiness of a public-key infrastructure depend on the technology, infrastructure, and practices of the certificate authority that issues and manages these certificates.. - Ensure that the CA’s own certificate is widely distributed. - Establishing trust among the members of the infrastructure. - Since the quality, efficiency and integrity of any PKI depends on the CA, the trustworthiness of the CA must be beyond reproach.. - On the one end of the spectrum, certain users prefer one centralized CA, which controls all certificates. - At the other end of the spectrum, some parties elect not to employ a central authority for signing certificates
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