Wiktionary
n. 1 (context physics English) The deflection of particles and/or radiation through angles greater than 90 degrees to the original direction of travel. 2 The particles and/or radiation deflected in this manner. 3 (context military English) A portion of the energy of electromagnetic radiation such as a laser or radio waves that is scattered back in the direction of the source of radiation by an obscurant. 4 (context computing English) The sending of IP packets to essentially random addresses in response to incoming packets that have a spoofed origin. vb. To scatter particles and/or radiation back to the direction from which they come.
WordNet
v. scatter (radiation) by the atoms of the medium through which it passes
Wikipedia
In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they came. It is a diffuse reflection due to scattering, as opposed to specular reflection like a mirror. Backscattering has important applications in astronomy, photography and medical ultrasonography.
Backscatter (also known as outscatter, misdirected bounces, blowback or collateral spam) is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.
Recipients of such messages see them as a form of unsolicited bulk e-mail or spam since they were not solicited by the recipients, are substantially similar to each other and are delivered in bulk quantities. Systems that generate e-mail backscatter may be listed on various DNS-based Blackhole Lists and may be in violation of internet service providers' Terms of Service.
Backscatter occurs because worms and spam messages often forge their sender address and a misconfigured mail server, which has Delivery Status Notifications enabled sends a bounce message to this address. This normally happens when a mail server is configured to relay a message to an after-queue processing step, for example, an antivirus scan or spam check, which then fails, and at the time the antivirus scan or spam check is done, the client already has disconnected. In those cases, it is normally not possible to reject at the SMTP stage, since a client would time out while waiting for the antivirus scan or spam check to finish. The best thing to do in this case, is then silently drop the message.
Measures to reduce the problem include avoiding the need for a bounce message by doing most rejections at the initial SMTP connection stage; and for other cases, sending bounce messages only to addresses which can be reliably judged not to have been forged, and in those cases the sender cannot be verified, thus ignoring the message (i.e., dropping it).
Backscatter is the reflection of waves, particles or signals. The term may also refer to:
- Backscatter X-ray, a new type of imaging technology
- Backscatter (DDOS), a side effect of denial-of-service attacks on computer resources
- Backscatter (email), a side effect of e-mail spam, viruses or worms
Usage examples of "backscatter".
Spock could just make out the backscatter glow of the images projected on the circular lenses.
She had no running lights, and her navigation beacon was off, but her distinctive lines were just perceptible in the backscatter of light from the night side of Remus.
The USMC goggles showed the pulse's backscatter as lavender shading on top of the thermal IR.
There weren’t many details, it was so dark, but the rim was close enough to see a silhouette of enticing geometries in the backscatter of red light.
A backscatter of stale light from the big mirror illuminated the sloping walls.
The power had been sundered to Manassas and the surrounding area, so the backscatter that was so difficult to avoid, that contributed at least an erg of illumination on the darkest night in the eastern United States, was entirely absent.
He was behind the blast shield, but anyone else nearby might be caught by backscatter as the plasma charge exited the spear slit.
Fred Singer of the Washington-based Science and Environmental Policy Project, who developed the principle of UV backscatter that the ozone monitoring instrument aboard Nimbus-7 employs.
It was so distant that it took on the milky backscatter color of the sky and it went up so high you literally couldn't see the top.
At first, he thought it was reflective backscatter from the X-ray source GED9287 was using to paint the target area, but the frequency was wrong, and the source far too intense.