Information
The user file-creation mode mask ( umask ) is used to determine the file permission for newlycreated directories and files. In AIX, the default permissions for any newly createddirectory is 0755 (rwxr-xr-x), and for any newly created file it is 0644 (rw-r--r--). The umask modifies the default AIX permissions by restricting (masking) these permissions.The umask is not simply subtracted, but is processed bitwise. Bits set in the umask arecleared in the resulting file mode.
Setting a very secure default value for umask ensures that users make a conscious choiceabout their file permissions. A default umask setting of 077 causes files and directoriescreated by users to not be readable by any other user on the system. A umask of 027 wouldmake files and directories readable by users in the same Unix group, while a umask of 022 would make files readable by every user on the system.
Solution
Add the umask attribute to the default user stanza in /etc/security/user :
chsec -f /etc/security/user -s default -a umask=027