-D [bind_address:]port
             Specifies a local “dynamic” application-level port forwarding.
             This works by allocating a socket to listen to port on the local
             side, optionally bound to the specified bind_address.  Whenever a
             connection is made to this port, the connection is forwarded over
             the secure channel, and the application protocol is then used to
             determine where to connect to from the remote machine.  Currently
             the SOCKS4 and SOCKS5 protocols are supported, and ssh will act
             as a SOCKS server.  Only root can forward privileged ports.
             Dynamic port forwardings can also be specified in the configura-
             tion file.

             IPv6 addresses can be specified by enclosing the address in
             square brackets.  Only the superuser can forward privileged
             ports.  By default, the local port is bound in accordance with
             the GatewayPorts setting.  However, an explicit bind_address may
             be used to bind the connection to a specific address.  The
             bind_address of “localhost” indicates that the listening port be
             bound for local use only, while an empty address or ‘*’ indicates
             that the port should be available from all interfaces.

E.g., if I wished to create a SOCKS proxy server at the SSH server end from an SSH client using the registered port commonly used as the listening port for a SOCKS proxy, i.e., TCP port 1080, I could use the command below, assuming that I have a jdoe account on the SSH server at example.com.

$ ssh -D 1080 jdoe@example.com

[ More Info ]

[/network/proxy] permanent link

Possibly some sectors on the memory card were damaged or the corruption could have been due to some other reason, but I thought I might be able to recover the images using a file repair tool. I tried the RS File Repair tool, which runs on Microsoft Windows systems, from Recovery Software, but the repaired files it generated were not useful.

[ More Info ]

[/reviews/software/windows/utilities/file] permanent link

As an example, suppose you are performing a traceroute between two computers with two routers between the source and destination systems as in the diagram below.

When you issue the command traceroute workstation2, the traceroute command will first send out a UDP datagram with a TTL of 1. Router 1 will decrement the TTL, at which point it becomes 0, so router 1 sends an ICMP "time exceeded" datagram back to workstation 1. Workstation 1 then sends another datagram to workstation 2, but this time with a TTL of 2. Router 1 is the first hop on the path to workstation 2 and it decrements the TTL and sends it on to router 2 which also decrements the TTL at which point it is now 0, so router 2 sends back a "time exceeded" datagram to workstation 1. Then workstation 1 sends a datagram with a TTL of 3. This time the TTL is decremented to 2 at router 1 and then to 1 at router 2, which sends the datagram on to workstation 2, which is the destination system that will send a reply back to workstation 1. On Microsoft Windows systems, the tracert command uses a similar process except it sends ICMP echo requests, instead of UDP packets to a high-numbered port.

Another tool available for use on Microsoft Windows systems is tcproute. Tcproute sends TCP packets to port 80 on the destination system, increasing the TTL value by one with each packet sent, so the tool is similar to the process employed by traceroute on Unix, Linux, or OS X systems, though it is using TCP rather than UDP and is using a destination port of 80, the default port used by web servers for Hypertext Transfer Protocol (HTTP) traffic.

[ More Info ]

[/os/windows/software/network] permanent link

$ ssh jdoe@example.com

But, if you just were logging in to enter one command, say you wanted to find the hardware platform of the remote system using the uname command uname --hardware-platform, you could simply append that command to the end of the above ssh command you would have used to log into the remote system. E.g.:

$ ssh jdoe@example.com uname --hardware-platform
jdoe@example.com's password: 
x86_64
$ uname --hardware-platform
i386

In the example above, issuing the same command on the local system, i.e., the one on which the SSH command is being issued shows that the result returned when the uname command was issued at the end of the ssh command line returned a result from the remote system.

You may even be able to use a text-based editor, such as the vi editor, though you may see error messages like the ones below:

$ ssh jdoe@example.com vi temp.txt
jdoe@example.com's password: 
Vim: Warning: Output is not to a terminal
Vim: Warning: Input is not from a terminal

When you enter an ssh command in the form ssh user@host the remote system allocates a pseudo-tty (PTY), a software abstraction used to handle keyboard input and screen output. However, if you request SSH to run a command on the remote server by appending that command after ssh user@host, then no interactive terminal session is required and a PTY is not allocated, so you see the error messages when you use a screen-based program intended for use with a terminal, such as the vi editor.

For such cases you should inclde the -t option to the SSH command.

E.g.:

$ ssh jdoe@example.com -t vi temp.txt

[/network/ssh] permanent link

TeslaCrypt underwent improvements in its own coding over time after first emerging in March 2015. It was originally developed to encrypt files associated with some computer games forcing players to pay a ransom in bitcoins, a preferred payment method for ransomware developers, because of its anonymity feature. Once a system was infected the ransomware would search for 185 file extensions related to 40 different games, including the Call of Duty series, World of Warcraft, Minecraft and World of Tanks and encrypt files so that players would be forced to pay a ransom to the TeslaCrypt developer(s) to unlock their data². Later the developers expanded the types of files that were encrypted to include Microsoft Word, PDF, and JPG files that would likely be found on nongamers' systems. When researchers for Cisco Systems Talos Group managed to develop a decryption tool for TeslaCrypt, the TeslaCrypt developer(s) released a version 2.0 of the ransomware so that the Talos Group tool could no longer be used to free victims from paying a $500 USD ransom to decrypt their files.

Later, in November of 2015, Kaspersky Lab researchers discovered a flaw in the 2.0 version of TeslaCrypt, which was corrected by the TelaCrypt developer(s) in a 3.0 release circulating as of January 2016.

On March 18 of 2016, version 4.0 of the ransomware was discovered. Researchers for the Danish security firm Heimdal Security published the security alert Security Alert: TeslaCrypt 4.0 – Unbreakable Encryption and Worse Data Leakage regarding enhancements to the malware that made it even harder to crack. The 4.0 upgrade also fixed a bug that would render files greater than 4 GB permanently unavailable even to those who paid the ransom. Morten Kjaersgaard, CEO of Heimdal, stated "They're really trying to make it like a product so when you do pay up you get your money's worth,"³ since ransomware developers know they won't be able to get new victims to pay the ransom if there are widespread reports by prior victims that they couldn't decrypt files even after paying the ransom. The 4.0 version of the ransomware also incorporated code to join infected computers into a botnet.

Now, though, with the release of a free, publicly available tool from ESET, which can be dowloaded from http://download.eset.com/special/ESETTeslaCryptDecryptor.exe, to decrypt files encrypted with TeslaCrypt using the master key, victims can unencrypt their files without paying a ransom.

References:

1. TeslaCrypt authors release master keys, Ransomware Info Day held 19 May
   By: Danielle Correa
   Date: May 20, 2016
   SC Magazine
2. TeslaCrypt
   Wikipedia, The Free Encyclopedia
3. TeslaCrypt 4.0 emerges; ransomware features tougher encryption, deeper penetration
   By: Bradley Barth, Senior Reporter March 21, 2016
   SC Magazine
4. Security Alert: TeslaCrypt 4.0 – Unbreakable Encryption and Worse Data Leakage
   By: Andra Zaharia
   Date: March 18, 2016
   Heimdal Security

[/security/ransomware] permanent link

1. Click on the Windows Start Button at the lower, left-hand corner of the screen or hit the Windows key.
2. Click on Settings.
3. Click on System.
4. In the System window, click on About. You will see the system name to the right of "PC name".

[ More Info ]

[/os/windows/win10] permanent link

So I took some pictures of the adapter for a new HP 15-af131dx notebook. I used a station my wife has in her studio for taking photos that has a white cloth for a backdrop and lights that are focused on the area to be photographed. But I used my cell phone to take the photos rather than the camera she uses. Even though I made some adjustments to the phone's settings for taking photos so that the images had a white background when I viewed them on the phone, when I uploaded them from the phone to a computer I found that the white backdrop looked somewhat gray when I viewed them on a couple of computers.

On my MacBook Pro laptop, I normally use the Preview program, which is found in the Applications directory on OS X systems, to view images. That application provides color adjustment capabilites that allowed me to easily adjust the colors in the image so that I got the whiter background I wanted for the images. After opening a photo in Preview, I could click on Tools then Adjust Color to bring up an Adjust Color window where I could change the following values for an image:

• Exposure
• Contrast
• Highlights
• Shadows
• Saturation
• Temperature
• Tint
• Sepia
• Sharpness

[ More Info ]

[/os/os-x/Preview] permanent link

[ More Info ]

[/os/os-x] permanent link

$ which gnome-screenshot
/usr/bin/gnome-screenshot

You can obtain help on using the tool to take a screenshot by typing gnome-screenshot at a shell prompt.

$ gnome-screenshot --help
Usage:
  gnome-screenshot [OPTION...] Take a picture of the screen

Help Options:
  -h, --help                     Show help options
  --help-all                     Show all help options
  --help-gtk                     Show GTK+ Options

Application Options:
  -c, --clipboard                Send the grab directly to the clipboard
  -w, --window                   Grab a window instead of the entire screen
  -a, --area                     Grab an area of the screen instead of the entire screen
  -b, --include-border           Include the window border with the screenshot
  -B, --remove-border            Remove the window border from the screenshot
  -d, --delay=seconds            Take screenshot after specified delay [in seconds]
  -e, --border-effect=effect     Effect to add to the border (shadow, border or none)
  -i, --interactive              Interactively set options
  --display=DISPLAY              X display to use

[ More Info]

[/os/unix/linux/utilities/graphics] permanent link

But there is an escape sequence that will allow me to terminate the current SSH session. Hitting the three keys listed below will allow me to terminate the session.

↲ Enter, ~, .

[ More Info ]

[/network/ssh] permanent link

$ sudo apt-get install ibmonitor
E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

I saw there was another installation in progress via the Update Manager, but the Update Manager update had been running for many days without successfully completing. I couldn't cancel or kill the Update Manager update through the graphical user interface (GUI) for the Update Manager, so I checked for any process identifier (PID) associated with update-manager.

$ ps -ef | grep -i update-manager | grep -v grep
jdoe      4339     1  0  2015 ?        00:02:24 /usr/bin/python /usr/bin/update-manager --no-focus-on-map
jdoe     14331     1  0 Apr17 ?        00:01:21 /usr/bin/python /usr/lib/update-manager/check-new-release-gtk
jdoe     25428     1  0 May01 ?        00:00:39 /usr/bin/python /usr/lib/update-manager/check-new-release-gtk

I killed all three of the processes I found associated with "update-manager", but that still did not allow me to successfully run apt-get.

[ More Info ]

[/os/unix/linux/ubuntu] permanent link

To install a .deb package with dpkg, you can use dpkg -i debFileName . You can obtain a list of the installed packages on a system with dpkg -l or dpkg -l [optional pattern] to filter the list of packages shown by an optional pattern.

I've never created a .deb package and was curious as to how to do so. I thought I'd start with something simple by creating a .deb package for ibmonitor, since the program is just one Perl script. To build the package, I followed the instructions in the How to Build section of Debian Packages.

[ More Info ]

[/os/unix/linux/ubuntu] permanent link

• Shows received, transmitted and total bandwidth of each interface
• Calculates and displays the combined value of all interfaces
• Diplays total data transferred per interface in KB/MB/GB
• Values can be displayed in Kbits/sec(Kbps) and/or KBytes/sec(KBps)
• Can show maximum bandwidth consumed on each interface since start of utility
• Can show average bandwidth consumption on each interface since start of utility
• The output with all features (max, avg and display in Kbps and KBps) easily fits on a 80x24 console or xterm
• Can interactively change its output display format depending on key pressed by user.

[ More Info ]

[/os/unix/linux/network] permanent link

If you need to transfer files between the local and remote systems, you can take the steps listed at Transferring Files Via the Remote Desktop.

[/os/windows/software/remote-control/rdp] permanent link

#!/bin/bash
# Bash Menu Script Example
PS3='Please enter your choice: '
options=("Option 1" "Option 2" "Option 3" "Quit")
select option in "${options[@]}"
do
case $option in
"Option 1")
echo "You chose option 1"
;;
"Option 2")
echo "You chose option 2"
;;
"Option 3")
echo "You chose option 3"
;;
"Quit")
echo "Quitting the program"
break
;;
*) echo invalid option;;
esac
done

Note: to make a script executable from your account, you must set the file permissions for the script to grant execute permission for your account, e.g. with chmod u+x menu, if the file name for the script was named menu.

When the script is run, it will display the following text:

1) Option 1
2) Option 2
3) Option 3
4) Quit
Please enter your choice:

If the person running the script types "1", the script will display "You chose option 1". It will display "You chose option 2", if he/she types "2", "You chose option 3", if he/she types "3" and, if he/she types "4", will display "Quitting the program" and then exit from the script. Hitting any other key will cause the script to display "invalid option" while allowing the user to type another key for one of the other options.

By setting the PS3 variable you can control the prompt that is displayed to the user. If it wasn't set, the user would see a default prompt, which is #?, displayed, instead, as shown below:

1) Option 1
2) Option 2
3) Option 3
4) Quit
#?

The select construct has the following format:

select Word in Array
do
  commands-for-options
done

Word and Array are names of your choosing. If you are unfamiliar with what an array represents, think of it as a collection of items. You can think of it as a list, though in computer programming languages those are not necessarily synonymous. You can find more information at Bash Arrays.

In the example above, I chose "Option" for Word and "Options" for the array name. The array, i.e., the list of options, was created with the following command:

options=("Option 1" "Option 2" "Option 3" "Quit")

The first element of the array, which contains 4 elements in this case, is "Option 1", the next "Option 2", etc.

The ${options[@] in select option in "${options[@]}" returns each item in the array as a separate word.

Between the case $option in and esac (case reversed), I can insert the commands to be carried out for each option that is selected. Including a *) allows the script to take some action when any key not associated with a valid option is typed. Each clause in the case statement must be terminated with ";;". Each case statement is ended with the esac statement. For further information on the case statement, see Using case statements in Machtelt Garrels Bash Guide for Beginners.

Bash is a common shell on Unix and Linux systems and is the default shell when you open the Terminal application on a Mac OS X system. And even Microsoft has announced that it will provide a Bash shell in the Windows 10 Anniversary Update, which is expected to be shipped this summer. So you can create text-based menus using this method on a variety of operating systems.

[/os/unix/bash] permanent link

Seq

$ seq 1 15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

[ More Info ]

[/os/unix/commands] permanent link

Later, when I had time to try to obtain some information on why it crashed, I checked the time it rebooted with last reboot.

$ last reboot | head -n 1
reboot    ~                         Thu May  5 12:26

When I looked for a crash report at that time in /Library/Logs/DiagnosticReports, I saw the folllowing file:

$ ls -l /Library/Logs/DiagnosticReports | grep '12:26'
-rw-rw----@ 1 root  admin     7905 May  5 12:26 Kernel_2016-05-05-122657_GSSLA15122293.panic

So it seemed the cause was a kernel panic, which occurs when the operating system detects an internal fatal system error from which it can't recover.

At OS X: When your computer spontaneously restarts or displays "Your computer restarted because of a problem.", Apple states:

Apple has information on how to interpret what you find in the crash log for an Intel-based system, such as a MacBook Pro, at How to Read the Panic Log from an Intel-Based Mac. That article indicates that you can determine the task name from which the current thread orginated from the line that begins with "BSD process name corresponding to current thread". Examining the crash report, I saw the following:

$ grep "BSD process name corresponding to current thread:" /Library/Logs/Diagnos
ticReports/Kernel_2016-05-05-122657_GSSLA15122293.panic
BSD process name corresponding to current thread: plugin-container

When I checked for any currently running processes associated with "plugin-container", I saw the following:

$ ps -ef | grep plugin-container | grep -v grep
723184451   982   509   0 12:49PM ??        14:40.67 /Applications/Firefox.app/C
ontents/MacOS/plugin-container.app/Contents/MacOS/plugin-container /Library/Inte
rnet Plug-Ins/Silverlight.plugin -greomni /Applications/Firefox.app/Contents/Res
ources/omni.ja -appomni /Applications/Firefox.app/Contents/Resources/browser/omn
i.ja -appdir /Applications/Firefox.app/Contents/Resources/browser 509 gecko-cras
h-server-pipe.509 org.mozilla.machname.902074418 plugin
$

I was using the Firefox web browser, version 38.7.0, at the moment the system crashed, so that application appears to have, indeed, been the culprit for the crash. I had a few Firefox windows and many tabs open when the system crashed. When I logged in after it rebooted, I reopened Firefox and chose to restore the prior session, but the system did not crash again after that today.

[/os/os-x] permanent link

[ More Info ]

[/software/database/sqlite] permanent link

Huber advised website owners using ImageMagick for image processing on their sites to check the magic number in uploaded image files to verify that an uploaded file is an image file. Wikipedia provides a list of common magic numbers at List of file signatures. One reason for ImageMagick's popularity is that it supports a large number of different file formats, supporting over 200 file formats. You can find a list of the supported file formats at ImageMagick: Formats. If you have ImageMagic installed, you can check on which formats it supports on the installed system by issuing the command identify -list format.

References:

1. Huge number of sites imperiled by critical image-processing vulnerability
   By: Dan Goodin
   Date: May 3, 2016
   Ars Technica

[/security/vulnerabilities] permanent link

[/network/routers/actiontec/MI424WR] permanent link