Monday, June 23, 2008
E-mail spoofing
Monday, June 16, 2008
Difficulties with e-mail forwarding

There are some additional details when an e-mail forwarder is involved. Forwarders perform a useful service in allowing you to have one simple permanent address, even if you change jobs or ISPs. List servers perform a similar function, forwarding e-mail to many receivers on behalf of one sender. Forwarders pose no problem for an end-to-end authentication method like DKIM and DomainKeys, as long as the signed message is not modified (some lists do this).
CSV limits its focus to one-hop authentications. SPF and SenderID have in essence the same limitation, they don't work directly behind the "border" ( MX ) of the receiver. For SPF forwarders to third parties could rewrite the Return-Path (MAIL FROM) in a similar way like mailing lists. This approach emulates the SMTP behaviour before RFC 1123 deprecated source routes; for a technical explanation see SRS.
For SenderID, forwarders to third parties and mailing lists are asked to add a Sender: or Resent-Sender: header. For many mailing lists, the former is already the case, but other forwarders avoid any modifications of the mail in addition to the mandatory Received-timestamp line.
Use of a forwarder prevents the receiver from directly seeing the sender's IP address. The incoming IP packets have only the forwarder's IP address. Two solutions are possible if one can trust all forwarders. Either one trusts the forwarder to authenticate the sender, or one trusts the forwarder to at least accurately record the incoming IP address and pass it on, so one can do their own authentication.
The situation gets complicated when there is more than one forwarder. A sender can explicitly authorize a forwarder to send on its behalf, in effect extending its boundary to the public Internet. A receiver can trust a forwarder that it pays to handle e-mail, in effect designating a new receiver. There may be additional "MTA relays" in the middle, however. These are sometimes used for administrative control, traffic aggregation, and routing control. All it takes is one broken link in the chain-of-trust from sender to receiver, and it is no longer possible to authenticate the sender.
Forwarders have one other responsibility, and that is to route Bounce messages (a.k.a. DSNs) in case the forwarding fails (or if it is requested anyway). E-mail forwarding is different from remailing when it comes to which address should receive DSNs. Spam bounces should not be sent to any address that may be forged. These bounces may go back by the same path they came, if that path has been authenticated.
Wednesday, June 11, 2008
Concurrent Versions System
Monday, June 02, 2008
Robot software
Some robot software aims at developing intelligent mechanical devices. Though common in science fiction stories, such programs are yet to become common-place in reality and much development is yet required in the field of artificial intelligence before they even begin to approach the science fiction possibilities. Pre-programmed hardware may include feedback loops such that it can interact with its environment, but does not display actual intelligence.
Currently, malicious programming of robots is of some concern, particularly in large industrial robots. The power and size of industrial robots mean they are capable of inflicting severe injury if programmed incorrectly or used in an unsafe manner. One such incident occurred on 21 July 1984 when a man was crushed to death by an industrial robot. That incident was an accident, but shows the potential risks of working with robots. In science fiction, the Three Laws of Robotics were developed for robots to obey and avoid malicious actions.
Tuesday, May 27, 2008
Ecological Systems Theory
* Microsystem: Immediate environments (family, school, peer group, neighborhood, and childcare environments)
* Mesosystem: A system comprised of connections between immediate environments (i.e., a child’s home and school)
* Exosystem: External environmental settings which only indirectly affect development (such as parent's workplace)
* Macrosystem: The larger cultural context (Eastern vs. Western culture, national economy, political culture, subculture)
* Chronosystem: The patterning of environmental events and transitions over the course of life.
The person's own biology may be considered part of the microsystem; thus the theory has recently sometimes been called "Bio-Ecological Systems Theory." Each system contains roles, norms, and rules that can powerfully shape development.
Monday, May 19, 2008
Evolutionary robotics
Monday, May 12, 2008
Software Innovation
Software Innovation can be understood in (at least) two ways:
2. Software Process Innovation - the introduction of novel and useful ways of developing software.
Tuesday, May 06, 2008
Cost overrun
Cost overrun is defined as excess of actual cost over budget. Cost overrun is also sometimes called "cost escalation," "cost increase," or "budget overrun." However, cost escalation and increases do not necessarily result in cost overruns if cost escalation is included in the budget.
Monday, April 28, 2008
Piri Reis map
The Piri Reis map ("Piri" pronounced /piɹi/) is a famous pre-modern world map created by 16th century Ottoman-Turkish admiral and cartographer Piri Reis. The map shows part of the western coasts of Europe and North Africa with reasonable accuracy, and the coast of Brazil is also easily recognizable. Various Atlantic islands including the Azores and Canary Islands are depicted, as is the mythical island of Antillia. The map is noteworthy for its depiction of a southern landmass that some controversially claim is evidence for early awareness of the existence of Antarctica.
Monday, April 21, 2008
Marine Cargo Types
* Containers are the largest and fastest growing cargo category at most ports worldwide. Containerized cargo includes everything from auto parts and machinery components to shoes, toys, and frozen meat and seafood.
* Automobiles are handled at many ports.
* Project cargo and heavy lift cargo may include items such as manufacturing equipment, factory components, power equipment such as generators and wind turbines, military equipment or almost any other oversized or overweight cargo too big or too heavy to fit into a container.
* Break bulk cargo is typically material stacked on wooden pallets and lifted into and out of the hold of a vessel by cranes on the dock or aboard the ship itself. The volume of break bulk cargo has declined dramatically worldwide as containerization has grown.
* Bulk Cargoes, such as salt, oil, tallow, and Scrap metal, are usually defined as commodities that are neither on pallets nor in containers, and which are not handled as individual pieces, the way heavy-lift and project cargoes are. Alumina, grain, gypsum, logs and wood chips, for instance, are bulk cargoes.
Monday, April 14, 2008
Logical schema
A Logical Schema is a data model of a specific problem domain that is in terms of a particular data management technology. Without being specific to a particular database management product, it is in terms of either (for example, in 2007) relational tables and columns, object-oriented classes, or XML tags. This is as opposed to a conceptual data model, which describes the semantics of an organization without reference to technology, or a physical data model, which describes the particular physical mechanisms used to capture data in a storage medium.
Monday, April 07, 2008
Apache Derby
Friday, April 04, 2008
Relational model
Monday, March 24, 2008
CrushFTP
Monday, March 17, 2008
Software development process
A growing body of software development organizations implement process methodologies. Many of them are in the defense industry, which in the U.S. requires a rating based on 'process models' to obtain contracts. The international standard for describing the method of selecting, implementing and monitoring the life cycle for software is ISO 12207.
Sunday, March 09, 2008
Building-integrated photovoltaics (BIPV)
Tuesday, March 04, 2008
Toxicity of Metabolites
Wednesday, February 27, 2008
Transreflective liquid crystal display
Transreflective liquid crystal displays use a retroreflector to transmit light when external sources of light are available, such as the sun or a lamp, and illuminate the screen well. When these sources are available but do not illuminate well, the display transmits its own light from a backlight at the rear of the display.
Friday, February 22, 2008
Materials intelligence and Air Sampling
One real-world example is a review of how xenon by-product levels could be used to distinguish if air sampling from a North Korean test, either atmospheric testing or leakage from an underground test, could be used to determine if the bomb was nuclear, and, if so, whether the Primary was plutonium or highly-enriched uranium (HEU)