If you've got a USB drive or SD card that can't be formatted and to which you can't copy files, then take a look at our guide to removing write protection.
Sometimes you'll find that it's impossible to format, delete or copy new files to an SD card or USB flash drive. Windows will tell you that it is write protected, even though there is no 'lock' switch or – if there is – you've made sure the switch is set correctly to allow files to be written to the drive.
But just in case this switch is news to you, it is well worth checking that your device has the switch set to 'unlocked'. When set to 'locked' you won't be able to copy any new files on to the memory card or USB stick, and it also stops you from accidentally formatting it.
You'll still be able to view files which are already stored on the drive, but you can't delete them (they sometimes seem to delete OK, but the next time you check, there they are again!).
ut if this isn't the problem, you might still be able to fix things and continue to use your USB flash drive or SD card – we'll explain how.
Unfortunately, in some cases the device may be corrupt or physically broken and no tricks or software will make it work again. The only solution in this case is to buy a new drive. And if you're just trying to get back lost data, see our guide on How to recover deleted filed for free.
In any version of Windows from XP onwards, run Regedit.exe.
If you're not sure how to find it, searching 'regedit' in the Start menu will usually show the program at the top of the list.
It's a bit like File Explorer, so use the pane on the left to navigate to the following key:
Note: if you can't find StorageDevicePolicies, see the next step.
Double-click on the WriteProtect value in the right-hand pane. You can now change the Value data from 1 to 0. Then click OK to save the change. Close Regedit and restart your computer. Connect your USB drive again and, with a bit of luck, you should find it is no longer write protected.
You can now continue to use the drive, but it's worth copying off any files you want to keep and then formatting it by right-clicking on it in the list of drives in File Explorer and choosing Format.
StorageDevicePolicies
If you can't find StorageDevicePolicies, you can create it by right-clicking in the white space in the 'Control' folder and choosing New -> Key and entering the name StorageDevicePolicies.
Now double-click on the new key (it will show as a folder) and right-click once again in the white space and choose New -> DWORD. Name this WriteProtect and set its value to 0. Click OK, exit Regedit and reboot your computer.
If this method doesn't work, go to the next step.
Diskpart
With your USB drive or memory card attached to your computer, launch a command prompt. You can do this by searching for cmd.exe or 'Command Prompt' in the Start menu.
Note: you may need to run cmd.exe with administrator privileges if you see an "access is denied" message. To do this, right-click on Command Prompt in the Start menu and choose 'Run as administrator' from the menu that appears.
If you have Windows 10, simply right-click on the Start button (bottom left of the screen) and choose Command Prompt (admin).
Now, at the prompt, type the following and press Enter after each command:
diskpart list disk select disk x (where x is the number of your non-working drive – use the capacity to work out which one it is) attributes disk clear readonly clean create partition primary format fs=fat32 (you can swap fat32 for ntfs if you only need to use the drive with Windows computers) exit
That's it. Your drive should now work as normal in File Explorer. If it doesn't, it's bad news and there's nothing more to be done. Your stick or memory card is scrap and fit only for the bin. But the good news is that storage is cheap.
A water softener is a device that removes hardness from water, typically by exchanging calcium and magnesium ions for sodium ions. This process, known as ion exchange, occurs within a resin bed, which is composed of small, porous beads made of a material called ion-exchange resin.
Why is a Water Softener Needed for Well Water?
Well water often contains high levels of dissolved minerals, including calcium and magnesium, which cause hardness. Hard water can create several problems, such as:
Scale Buildup: Hard water can cause scale buildup in pipes, appliances, and fixtures, reducing their efficiency and lifespan.
Soap Scum: Hard water can make it difficult to create a lather with soap, resulting in soap scum buildup on surfaces.
Dry Skin and Hair: Hard water can strip away natural oils from skin and hair, leading to dryness and irritation.
Reduced Detergent Effectiveness: Hard water can reduce the effectiveness of detergents, making it harder to clean clothes and dishes.
Water Hardness Level: The first step in choosing a water softener is to determine the hardness level of your well water. There are several ways to do this, including purchasing a water test kit or sending a sample of your water to a laboratory for analysis.
Flow Rate: Consider the flow rate of your well water system when selecting a water softener. The flow rate is measured in gallons per minute (GPM) and determines the size of the water softener you need.
Grain Capacity: The grain capacity of a water softener refers to its ability to remove hardness from water. The grain capacity is measured in kilograins (KGR) and determines how much hardness the water softener can remove before it needs to be regenerated.
Type of Water Softener: There are two main types of water softeners: salt-based and salt-free. Salt-based water softeners use a process called ion exchange to remove hardness from water, while salt-free water softeners use a different process, such as template-assisted crystallization.
Brand and Reputation: Consider the brand and reputation of the water softener manufacturer when making a purchase. Look for brands that are known for their quality, reliability, and customer service.
Proper Installation: It is important to have a water softener installed by a qualified professional. Improper installation can lead to leaks, damage to the water softener, or ineffective water softening.
Regular Regeneration: Water softeners need to be regenerated regularly to maintain their effectiveness. The frequency of regeneration depends on the hardness of your water and the size of the water softener.
Salt Replenishment: Salt-based water softeners require regular replenishment of the salt supply. The frequency of replenishment depends on the hardness of your water and the size of the water softener.
Maintenance: Water softeners should be inspected and maintained regularly to ensure proper operation and longevity. This may include cleaning the resin bed, checking for leaks, and replacing any worn or damaged parts.
Improved Water Quality: Treated water has a reduced mineral content, improving the taste, smell, and appearance of the water.
Reduced Scale Buildup: This can save you money by extending the lifespan of your appliances.
Softer Skin and Hair: Softened water can help to improve the health of your skin and hair.
More Effective Laundry and Dishwashing: Softened water can improve the performance of detergents and soaps.
Increased Energy Efficiency: Softened water can help to improve the efficiency of water heaters and other appliances that use water.
Conclusion:
A water softener can be a valuable investment for well water users, providing numerous benefits and improving overall water quality. By choosing the right water softener and properly installing and maintaining it, you can enjoy the advantages of softened water throughout your home.
Microsoft on Wednesday shed light on a previously undocumented Mac trojan that it said has undergone several iterations since its first appearance in September 2020, effectively granting it an "increasing progression of sophisticated capabilities."
The company's Microsoft 365 Defender Threat Intelligence Team dubbed the new malware family "UpdateAgent," charting its evolution from a barebones information stealer to a second-stage payload distributor as part of multiple attack waves observed in 2021.
"The latest campaign saw the malware installing the evasive and persistent Adload adware, but UpdateAgent's ability to gain access to a device can theoretically be further leveraged to fetch other, potentially more dangerous payloads," the researchers said.
The actively in-development malware is said to be propagated via drive-by downloads or advertisement pop-ups that masquerade as legitimate software like video applications and support agents, even as the authors have made steady improvements that have transformed UpdateAgent into a progressively persistent piece of malware.
Chief among the advancements include the capability to abuse existing user permissions to surreptitiously perform malicious activities and circumvent macOS Gatekeeper controls, a security feature that ensures only trusted applications from identified developers can be installed on a system.
In addition, UpdateAgent has been found to take advantage of public cloud infrastructure, namely Amazon S3 and CloudFront services, to host its second-stage payloads, including adware, in the form of .DMG or .ZIP files.
Once installed, the Adload malware makes use of ad injection software and man-in-the-middle (MitM) techniques to intercept and reroute users' internet traffic through the attacker's servers to insert rogue ads into web pages and search engine results to increase the chances of multiple infections on the devices.
"UpdateAgent is uniquely characterized by its gradual upgrading of persistence techniques, a key feature that indicates this trojan will likely continue to use more sophisticated techniques in future campaigns," the researchers cautioned.
Integer overflow and underflows often occur when user supplied data controls the value of an unsigned integer. The user supplied data either adds to or subtracts beyond the limits the variable type can hold. If you remember back to your computer science class, each variable type can hold up to a certain value length. You will also remember some variable types only hold positive numbers while others hold positive and negative numbers. The types of numbers they are allowed to hold is based on their "signedness." An unsigned integer can only hold positive numbers while a signed integer can hold positive and negative numbers. We will get to the significance of that in a short bit.
If you violate the value constraints of the variable type you are using, the application may act in unintended ways. For example, the overflow may result in an error condition for accessing out of bounds items or perhaps cutting the number off at the maximum or minimum value. This usually depends on the language in use, the context in which the value is used or the decisions taken by the programmer when flagging error conditions. If un-handled, the error from an attacker's perspective is usually an opportunity for exploitation.
For example, if you were calculating a number for an authorization check within an application and the calculation contains an unchecked value with user-controlled data. Then an attacker may be able to bypass authorization restrictions with that user-controlled data and gain additional access to unintended services. For example, overflowing a larger unsigned value to a more advantageous value, such as zero or one, these lower values could bypass security checks. The first ("1") value in a dataset is often indicative of an administrator who set up the application and may create a situation to persist actions with administrative context.
In the Solidity language for Ethereum, when we overflow a uint value using a value larger than our uint can hold, the value wraps back around to a number it understands. The lowest or highest possible value the uint can hold. For example, if we have a variable that can only hold a 2-digit number when the number 99 is reached and then incremented one more time, we will end up with 00. Inversely if we had 00 and we decremented 1 we would end up with 99.
Normally in your math class the following would be true:
99 + 1 = 100
00 - 1 = -1
In solidity with unsigned numbers the following is true:
99 + 1 = 00
00 - 1 = 99
So, the issue lies with the assumption that a number will provide a correct value in mathematical calculations when indeed it does not. Comparing a variable with a require statement is not sufficiently accurate after performing a mathematical operation that overflows a value, but that does not check that the value is accurate in the context of the mathematical operation.
In an overflow conditions the comparison with a require statement may very well be comparing the output of an over/under flowed value and be completely meaningless. The "Require" statement may return true, but not based on the actual intended mathematical value.
This in turn will lead to an action performed which is beneficial to the attacker, for example, checking a low value required for a funds validation but then receiving a very high value sent to the attacker after the initial check. Let's go through a few examples.
Simple Underflow Example:
Let's say we have the following Require check as an example:
1.require (balance - withdraw_amount > 0);
Now the above statement seems reasonable, if the users balance minus the withdrawal amount is less than 0 then obviously, they don't have the money for this transaction correct?
This transaction should fail and produce an error because not enough funds are held within the account for the transaction. But what if we have 5 dollars and we withdraw 6 dollars using the scenario above and our variable can hold 2 digits with an unsigned integer?
Let's do some math.
5 - 6 = 99
Last I checked 99 is greater than 0 which poses an interesting problem. Our check says we are good to go, but our account balance isn't large enough to cover the transaction. The check will pass because the underflow creates the wrong value which is greater than 0 and more funds then the user has will be transferred out of the account.
The below example snippet of code illustrates a withdraw function with an underflow vulnerability:
1.function withdraw(uint _amount){
2.require(balances[msg.sender] - _amount > 0);
3. msg.sender.transfer(_amount);
4. balances[msg.sender] -= _amount;
5. }
In this example, the require on line 2 checks that the balance is greater than 0 after subtracting the _amount. However, if the _amount is greater than the balance, it will underflow resulting in a large value greater than 0. So even though the require check should fail the check will return a true value.
After the check is under flowed, it will send the value of the original _amount on line 3 to the recipient without any further checks resulting in sending more funds then the user has.
To make matters worse, on line 4 another underflow exists, which increases the value of the senders account due to a similar underflow condition, even though the balance should have been reduced based on application logic.
Depending on how the "require" check and transfer functions are coded, the attacker may not lose any funds at all, while still transferring large sums of Ether to other accounts under the attacker's control. The attacker would achieve this by simply under flowing the require statements which checks the account balance before transferring funds each time.
Overflow conditions often happen in situations where you are sending a batched amount of values to multiple recipients. If you are performing an airdrop, sending tokens to 200 users, each receiving a large sum of tokens, checking the total sum of all users' tokens against the total funds may trigger an overflow. The logic when overflowed would compare a smaller value of overflowed tokens to the total tokens and seem like you have enough to cover the transaction.
For example, if your integer can only hold 5 digits in length or 00,000 what would happen in the below scenario?
You have 10,000 tokens in your account
You are sending 200 users 499 tokens each
Your total sent is 200*499 or 99,800
The above scenario should fail, and it does, since we have 10,000 tokens and want to send a total of 99,800. But what if we send 500 tokens each? Let's do some more math and see how that changes the outcome.
You have 10,000 tokens in your account
You are sending 200 users 500 tokens each
Your total sent is 200*500 or 100,000
New total is actually 0
This new scenario produces a total that is 0 even though each users amount is only 500 tokens. This may cause issues if a require statement is not handled with safe math functions to sanitize the mathematical output.
Let's take our new numbers and plug them into the below code and see what happens:
1: The total variable equals 100,000 which becomes 0 due to the 5-digit limit. When a 6th digit is hit at 99,999 + 1 the total now becomes 0.
2: This line checks if the users balance is higher than the total value to be sent. Which in this case is 0 so 10,000 is more than enough and this check passes due to the overflow.
3: This line deducts the total from the sender's balance which does nothing since the total of 10,000 - 0 is 10,000. The sender has lost no funds.
4-5: This loop iterates over the 200 users who each get 500 tokens and updates the balances of each user individually using the real value of 500 and this individual action does not trigger an overflow condition. Thus, sending out 100,000 tokens without reducing the sender's balance or triggering an error due to lack of funds. This is essentially creating tokens out of thin air.
In this scenario the user retained all of their tokens but was able to distribute 100k tokens across 200 users regardless if they had the proper funds to do so.
Now that we understand what overflows and underflows are, we are going to take a closer look at a real-life hyperinflation attack from 2018. When a bunch of erc20 tokens incorrectly checked the results of mathematical calculations. This lack of safe checks led to exchanges freezing all erc20 token transfers. We will first exploit this code from the original attack. We will then re-code the smart contract to protect against this attack.
The effected tokens in this attack used an insecure batch send function that was not protected from integer overflows. This is similar to our batch send example above. This vulnerability was copy pasted into many different tokens and when exploited it forced exchanges to suspend all erc20 token transfers until the issue was resolved.
üLet's first pull down the code and take a look at the vulnerable function. üThen we will take a look at the actual payload on etherscan from the real attack to decipher
how it happened. üThen we will exploit it ourselves. üThen we will fix the issue and test our fix.
Action Steps:
üReview the following lines of code and see if you can spot the vulnerability
üFollow the attack on EtherScan and understand how the attack works
üThen watch the video walk and talk to solidify the process
Below is the function from the ERC20 contract which had the initial vulnerability. Also, a link to view the code for yourself on etherscan. Just do ctrl+f search for the batch transfer function on the contract page.
The issue with this function is it's performing a balance check against the amount on line 5 but that amount value comes from a mathematical operation on line 3 which has an overflow vulnerability.
You will see that the amount results from multiplying the length of the array times the value being sent. Since there are no checks that this mathematical operation does not overflow to a value lower than our balance, we can easily set the amount to 0 using a very large number as our _value.
When the actual balances are updated on line 10, we are not using the amount of 0, but instead we are using the initial large _value sent to the function, but this time there is no multiplication, so it does not cause an overflow, it only updates the value to a very large number.
Now let's take a look at an actual transaction that caused this overflow attack.
Below is the transaction from the overflow attack. Also, a link to view the transaction for yourself on etherscan. Just click the "click to see more" button and check out the "input data" section.
If you reviewed the transaction on chain you would see the above transaction data.
Let's go into a little detail as to what the transaction values are and how they were derived. This will help in understanding what is going on with this attack.
The data in the transaction can be broken down as the following
üA 4byte MethodID
üFive 32-byte values
The 4-byte MethodID which precedes the function parameters is the first 4 bytes of a sha3 hash of the batchTransfer method declaration minus the variable names and spaces. We can derive this sha3 value from the transaction by using the web3 utility functions and a substring of the sha3 output.
You can try this out with the following node commands.
The 5 parameters following the MethodID are defined as follows:
[0] Offset to the _recievers Array, length value: 40Hex or 64 bytes (2x32 = 64bytes to the Array length held at [2])
[1] This is the actual _value which is being sent that when multiplied causes an overflow. (A very large number)
[2] This is the size of the _recievers array sent to batch transfer in this case 2 addresses
[3] This is the first address from the _recievers array used in the batch transfer.
[4] This is the second address from the _recievers array used in the batch transfer.
Reviewing a Live On-Chain Attack Transaction:
So, what this attack did was take a very large value from [2] and multiplied it times the length of the array which is the value 2. This creates an overflow condition that results in the value of 0. Don't believe me, let's do it for ourselves with a simple function that calculates the value sent times two.
1.pragma solidity ^0.6.6;
2.
3.contract noAuth {
4.function amount(uint256 myAmount) public returns(uint){
5.return myAmount * 2;
6. }
7.}
Action Steps:
üDeploy the contract from above.
üFirst put in a low number like 5 and review the output window, what do you get?
üNow put in the attack value in hex for aka 0xnumber 0x8000000000000000000000000000000000000000000000000000000000000000
üWhat happened?
As you will see an amount of 0 results which will pass the checks allowing an attack to work. Resulting in a very large value sent as the _value variable to the user. Causing hyperinflation of the token.
This is pretty cool, but let's actually exploit this attack ourselves. I have taken the liberty of updating the function from Beauty Chain to meet the current compiler standards with a few small tweaks and some functions so you can check your balance during the stages of the attack. Deploy this contract and try to exploit it before reading the walkthrough!!
For this one you can type it out for practice or grab it from the github folder since this is a case study and not the normal learning material per say. I will allow laziness this one time.
I slightly modified the vulnerable function from beautychain to work with the newer versions of solidity by adding in a few keywords and new syntax but this is basically the same code. Solidity requirements have changed a lot since version 4 when this was originally deployed. So I updated it to make it so you could actually deploy it without any issues in a newer version and learn the differences between versions.
Action steps:
üUsing account 1 deploy the BEC_Vuln Contract and deposit some wei, maybe 2000.
üCheck the value of account 1, account 2 and account 3.
üSend the attack from account 1 and perform a batch transfer by sending in an array of 2 addresses followed by the attack value in hex. See the below example for reference.
üNow check the values of the 3 accounts, what are they? What happened?
Now let's take a quick look at fixing issues related to integer overflows and underflows. As always in application security, we should not try to roll our own security libraries. We should instead use opensource well vetted security libraries for coding projects. Ethereum is no exception to this rule and has its own opensource libraries from OpenZeppelin which handle anything from safe mathematical calculations to role based authentication. Below is a direct link to the safe math library you will now import into your BEC_Vuln.sol file and then fix the current overflow issues.
We will do this by using the following line under ae pragma solidity definition
pragma solidity 0.6.6;
import"PASTE OPENZEPPELIN LINK HERE";
With this import statement we will now have access to the math functions within safe math for example:
üAdd
üSubtract
üMultiply
üDivide
These functions can be accessed with dot notation. For example in the following:
SafeMath.mul(value1, value2)
Action Step
üLocate all of the mathematical functions in the example
üRe-code all of them to match the above format
üTry your attack again, results?
üHow many did you find and update?
üWhat happened when you ran the attack again?
Safe Math Walk Through
We need to update all of the mathematical functions within our contract and then try our attack again. First try to locate all of these and update them according to the type of mathematical calculation.
You should have found 3 locations which need updating to comply with safe math standards These are shown below with the correct syntax needed to fix them with OpenZeppelin. Apply these changes to your code if you have not already.
If you apply the above fixes within your code then the returned values of the mathematical operations are double checked to make sure they make sense. For example, check out the OpenZeppelin code for multiplication:
1.function mul(uint256 a, uint256 b) internal pure returns (uint256) {
2.if (a == 0) {return0;}
3.
4. uint256 c = a * b;
5.require(c / a == b, "SafeMath: multiplication overflow");
6.return c;
7. }
Note that 2 parameters are taken into the function on line 1 which are our two values we are multiplying together. In our case our number of addresses in the array and the _value to send. These values are multiplied on line 4 and stored in the value c.
Then on line 5 the reverse operation Is performed on the result, dividing the returned value c by a and requiring that it is equal to the value of b. If this was an overflowed and wrapped around back to 0 then this check would obviously fail as the number would be incorrect.
If this check fails an error condition is shown like the following:
If this check passes then the transaction finishes as normal and the transaction completes as intended. Make sure that you re-code this and then run the attack again yourself. Review the output from the transactions for both. Also review the Add and the Subtract functions, which you also re-coded and make sure you understand how they are working as well.
You can find the open zeppelin code at the link where you imported if from, or within remix where it was imported to a github folder path. Review the code and use the functions in your applications to protect against math issues. If you are a penetration tester make sure that the contracts you are reviewing are using safe math functions whenever math is used.
Using OpenZeppelin Safe Math Libraries To Prevent Integer Attacks:
We went through what might have been an overwhelming number of concepts in this chapter regarding over/underflow scenarios. Make sure that you type out each of the examples and execute the code to understand what the issue is and how to spot it. Then re-code the examples to fix the issues.
