tailieunhanh - Implementing Database Security and Auditing phần 4

Sau đó đến heap, phát triển từ các địa chỉ thấp đến các địa chỉ cao. Nếu bạn liên tục phân bổ các biến trên heap, họ sẽ ngày càng sống trong bộ nhớ cao hơn. Bởi vì cả hai heap và stack có thể phát triển động (heap khi bạn cấp phát bộ nhớ hơn và ngăn xếp khi bạn thực hiện cuộc gọi chức năng hơn), hệ thống điều hành tối đa hóa việc sử dụng bộ nhớ (và giảm thiểu công việc nó đã làm). | 114 Choose strong passwords Let s move on to password checking tools. You can use a tool such as SQLdict but this is not very effective. It is slow and it creates a lot of noise . if you are alerting based on excessive failed logins you will be spending the next five years deleting e-mails . From a performance standpoint going through a dictionary with 100 000 words could take almost a full day. Instead you can use a class of tools that run within the database and that use the fact that they have access to the database table where the password hashes are stored. If you are running SQL Server you can use the SQL Server Password Auditing Tool which is available at id 10. The tool assumes that you give it a text file with the usernames and password hashes as stored in the sysxlogins table. After downloading the tool you should extract this information using select name password from and export it to a comma-delimited text file called . You then run the tool from the command line using sqlbf -u -d -r The tool is very fast. On my machine it made more than 200 000 guesses per second. You can also run a brute-force attack instead of a dictionary attack by running sqlbf -u c -r The c flag tells the tool that the .cm file is a character set file. The default English file has the following character set and you can change it if you have another locale ABCDEFGHIJKLMNOPQRSTUVXYZ0123456789 If you have an Oracle environment you also have an abundance of tools. You can use any of the following tools to do password checking Oracle Auditing Tools OAT is a set of tools that you can download from id 7. Among the tools is OracleP-WGuess which is a dictionary attack tool. Choose strong passwords 115 Oracle Password Cracker by Adam Martin seems to be no longer available but if you can find the download site it is a nice tool to have. .