Tech Tip: How to clean out the Windows Hosts file if malware has tampered with it

Viruses attack computers not just by posting pop-up ads for phony software. They also cripple the computer's basic functions so that the virus is difficult to get rid of. One of the chief objectives of viruses is to prevent internet browsers from going to web sites chosen by the user. There are several ways that viruses steer a browser away from its intended destination. Sometimes they install a Proxy Server into the web browser (See Part 3 in this series, "How to clear the Proxy Server setting"). At other times a virus will insert unwanted IP addresses into the network settings (See Part 4 in this series, "How to reset Static IP addresses to dynamic IP addresses"). A third way that viruses hijack internet connections is rarer, but it does happen. If previous attempts at solving the problem do not work, it is worth investigating a Windows feature called the Hosts file.

The WindowsHosts file serves to map user-friendly and familiar web site addresses (such as Google) to the actual IP addresses that are behind such names (such as 216.239.51.99). The Hosts file is sometimes used by network administrators for managing fixed networks. Unfortunately, it is also a target for viruses that want to hijack a computer's internet connectivity. Fortunately, however, if the Hosts file has been attacked and unwanted material written into it, the file can be manually cleaned.

The Hosts file is located deep in the Windows folder. It is not easy to find, but following these steps will help you locate it, inspect it and-if necessary-clean it up.

First, you need to open up the Windows text editor called Notepad. (For Windows Vista, 7 and 8, this needs to be launched with administrator privileges.) Depending on which version of Windows you have, this is done differently:

1) In Windows XP:

• Click on the Start button
• Click the Run button in the menu
• Type notepad in the box, hit the Enter key
  
  

2) In Windows Vista:

• Click on the Start button
• Type notepad in the search box
• Right-click the Notepad program in the list
• Click Run as administrator in the drop-down menu
• Click Yes to allow the program to make changes (if this option appears on the screen)
  
  

3) In Windows Vista:

• Click on the Start button
• Type notepad in the search box
• Right-click the Notepad program in the list
• Click Run as administrator in the drop-down menu
• Click Yes to allow the program to make changes (if this option appears on the screen)
  
  

4) In Windows 8:

• Open the Charms menu and click on the Search Charm
• Type “notepad” in the Apps search window
• Right-click the program Notepad that appears in the results in the upper left corner
• In the taskbar that opens at the bottom of the screen, click Run as administrator
• Click Yes to allow the program to make changes (if this option appears on the screen)

When notepad is opened up, you will see a new window for the Notepad text editor that looks like this:

 

With the Notepad application open click on File in the menu bar, then click on Open in the drop-down menu (as indicated by the red arrow, above).

To locate the Hosts file, start with a double-click on the C drive in the left panel, then the Windows folder, the System32 folder, the drivers folder, and finally the etc folder. Once the etc folder is open, click on Text documents (*.txt) and drop down to the next option which is All files (*.*). If you are in the correct folder, you will see a list of 3 to 5 files in the window, as shown below. Now, double-click the Hosts file (circled) to open it up in the text editor.



The example below is of an actual hijacked Hosts file. All the lines of text that are preceded by the # sign are legitimate (comments). All the others were inserted by a virus to steer users in various countries to the unintended IP address of 74.50.127.5 (the web site designed by the virus author) instead of Google.



To remove the intruding instructions in the host file is simply a matter of deleting the lines that are not wanted. Using Notepad, move the cursor to the area (as highlighted, above) and delete those lines, leaving the original lines in the Hosts file.

A clean Hosts file will look something like this:

When finished editing, simply save the file, reboot the computer, and try to use your browser normally. Hopefully, the experience of being steered away from desired web sites will be gone, and you will be able to browse freely.

For more assistance contact Technical Support here.

Tech Tip: How to fix internet connection problems

Everyone who uses the internet experiences connection problems from time to time. The "Cannot display the web page" message in Internet Explorer, or the "Server not found" message in Firefox, or the "Ooops!" message in Google Chrome are familiar but unwanted sights. In each case, you're going nowhere on the web. Sometimes the connection problem is caused by hardware issues: a computer adapter malfunction, a modem or router that has finally burned out, or a broken wire or loose cable. Very often, however, there are software issues that cause the connection problem. Many of these issues can be addressed with just a little bit of technical know-how. This series of how-tos is designed to help you try some of the most common software fixes for internet connection problems. The series includes:

1. How to find a Wireless Access Point before launching a browser
2. How to make sure your network adapter is working and has a software driver
3. How to clear the Proxy Server setting in Internet Explorer
4. How to reset static IP addresses to dynamic IP addresses
5. How to clean out the Windows Hosts file if malware has tampered with it

For more assistance contact Technical Support here.

MiniPingBot Construction

This small Arduino obstacle-avoiding robot is an experiment in reducing 

the size and complexity of larger kit and Do It Yourself (DIY) robots.

Bot Mechanics:
I started with an enclosed 4-cell AA battery pack. This had an advantage of having a small slide switch mounted in the case, so you don't have to keep disconnecting the power connector.
Two mini (9g) continuous rotation servo motors (RobotShop.com ~$5 / ea.) were attached to the back of the battery case using double-stick foam tape. Hot glue further secures the motors to the case, but probably is not needed as long as the tape is reasonably fresh and tacky.
A pair of small wheels off of a toy car were hollowed out, and were the perfect size for the round disk servo horn. The horn disk was press-fit into the wheel and super-glued in place. Hot glue on the inside of the wheel adds additional support between the disk and the inside surface.
A breadboard was trimmed down on the band saw to make a better fit, and the double-stick foam backing used to anchor the board to the lid of the battery box.
A piece of 1/8" plastic sheet was trimmed to make a mount for a 4-pin ultrasonic sensor module. Using a pencil, the position of the two cylindrical sensors was marked out on the plastic, and holes cut using a Dremel tool with a multi-purpose routing drill. A small piece of sticky-back Velcro helps space the sensor from the plastic and help hold it in place. Two O-rings are added to hold the sensors in the openings. A bead of hot glue was run along the edge of the breadboard and two small screws anchor the sensor assembly securely to the bot.
For the front wheel, a tiny ball-bearing was screwed to the battery box. (The front end of the box is mostly empty space, so there is no chance of shorting the batteries.) A hunt in the junk box came up with a small wheel assemble from some old printer parts, and a valve stem cap from a bicycle tire that fits over the bearing perfectly. A little cutting and sanding of the plastic frame with the tiny wheel, and then the two parts were glued together with more hot glue.
Bot Electronics:
The Arduino Nano connects directly into the breadboard. This is mounted at the rear of the board to allow access with the USB cable for programming the bot. A ground wire is connected between one of the negative rails and the "GND" pin on the Nano. Power is provided by a wire running from "VIN" on the Nano to the positive 5v rail.
The power wires from the battery pack are cut off close to the front of the breadboard. The positive (red) and negative (black) wires are each soldered to a pair of pins in a 2x2 connector and hot glue used to insulate the exposed pins. This fabricated connector plugs into one of the power rails of the breadboard. (This will be our 6v rail - assuming there are four 1.5v Alkaline batteries in the box)
A 5v regulator has the input pin bent out and a red wire soldered to it. (Hot glue can coat the exposed pin, or use a small piece of heat-shrink tubing to cover it.) The center pin (ground) and 5v output pin are trimmed off and inserted directly into the second power rail of the breadboard. (Note that this step is probably not required, but was done only as a precaution to provide 5v or less for the ultrasonic sensor and Arduino boards.) The red wire has the end soldered to a single pin or is stiffened by tinning the end with solder. This is then connected to the positive side of the 6v rail from the batteries. A wire connects both negative (ground) rails together.
Servo Motor wires have the signal wire split off and the power wires trimmed shorter. Another 2x2 pin connector has the two servo motor ground wires soldered on, and the two power wires soldered on the remaining two pins. Hot glue to insulate, and then the servo motor power is connected to the 6v rail. The two signal wires from the servo motors have enough reach to be connected to any of the Arduino pins. These each have a small pin soldered to the end and insulated with hot glue. Servo motor signal wires are attached to Arduino D10 and D11.
A four-wire connector is prepared for the sonar module. The outside power (Vcc and Gnd) connections are soldered to a pair of pins and connected to the 5v power rail. The inside pair of pins (Trig and Echo) are soldered to another pair of pins and connected to D5 and D6.

Programming:

Sample sketches are included. MiniPingBot1_0.ino is the first attempt to create a very simple program that uses a single ping to check distance. Then, based on the result, it moves forward, or if it detects an obstacle close by, backs up, rotates to the left and continues. This sketch is using the NewPing library and the core routines from the whisker-bot sketch from Parallax.

#include <NewPing.h> // include new-ping library #include <Servo.h> // Include servo library #define TRIGGER_PIN 5 // using 4-pin Ping Sensor #define ECHO_PIN 6 #define MAX_DISTANCE 200 // max distance is 500cm (~16.4 ft) Servo servoLeft; // Declare left and right servos Servo servoRight; NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); //declare sonar (ping sensor) void setup() { servoLeft.attach(10); // Attach left servo signal to pin 13 servoRight.attach(11); // Attach right servo signal to pin 12 //Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results } void loop() { delay(50); //wait 50ms between pings int uS = sonar.ping_cm(); // get distance in cm from sensor // based on distance, do something... // if uS = 0 distance to object is >= MAX_DISTANCE //Serial.print("Ping: "); // Monitor ping results in //Serial.print(uS); // serial monitor window //Serial.println("cm"); // comment out when done debugging if (uS > 30) { forward(300); // forward 1/2 second } else { backward(100); // obstacle detected closer than MAX_DISTANCE turnLeft(400); // try turning left a bit and check again } } // Servo control from Parallax BOE-Bot Whisker sketch void forward(int time) // Forward function { servoLeft.writeMicroseconds(1700); // Left wheel counterclockwise servoRight.writeMicroseconds(1300); // Right wheel clockwise delay(time); // Maneuver for time ms } void turnLeft(int time) // Left turn function { servoLeft.writeMicroseconds(1300); // Left wheel clockwise servoRight.writeMicroseconds(1300); // Right wheel clockwise delay(time); // Maneuver for time ms } void turnRight(int time) // Right turn function { servoLeft.writeMicroseconds(1700); // Left wheel counterclockwise servoRight.writeMicroseconds(1700); // Right wheel counterclockwise delay(time); // Maneuver for time ms } void backward(int time) // Backward function { servoLeft.writeMicroseconds(1300); // Left wheel clockwise servoRight.writeMicroseconds(1700); // Right wheel counterclockwise delay(time); // Maneuver for time ms }

MiniPingBot1_1 changes the method of determining distance with the sensor. One problem I noticed with the 1.0 version of the code was that the ping sensor would occasionally return a bad value and cause the bot to correct multiple times, even when no obstacle was close. Using the PING_MEDIAN function, five pings are used and the median result is returned to the program. This seems to eliminate the odd course corrections.

int uS = sonar.ping_cm(); // get distance in cm from sensor uS using single ping becomes: unsigned int uS = (sonar.ping_median() / US_ROUNDTRIP_CM); // Get average distance for 5 pings, convert to cm // US_ROUNDTRIP_CM = distance sound travels in cm/sec

MiniPingBot files (zip) <== Click to download the MiniPingBot 1.0 & 1.1 sketch files and NewPing library. To use: extract the contents of this zip file to your Arduino working directory. Open the containing folder for the Arduino.exe program and locate the "libraries" subdirectory. Copy the entire "NewPing" folder into the libraries directory.

For more assistance contact Technical Support here.