Category Archives: coding

3D Matrix Multiplication Tricks

Recently, I came across times 3D matrix multiplication in Matlab. It is for frequency domain signal processing, specifically, frequency-dependent multi-channel Wiener filter. Here, 3D matrix multiplication means 2D matrix multiplication at each frequency (or other parameters):  Given and which are … Continue reading

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Blacklist IPs that attack SSH and FTP services on a Linux machine

I manage a Linux server (Redhat EL4, kernel version 2.6.9-34). Yesterday,  I found the server was attacked relentlessly from It seemed to be a brutal force dictionary attack. What to do then? The obvious way is to manually add that IP … Continue reading

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