Chapter 10: Information System Controls for System Reliability Part 3: Processing Integrity and Availability

Transcription

1 Chapter 10: Infrmatin System Cntrls fr System Reliability Part 3: Prcessing Integrity and Availability Cntrls Ensuring Prcessing Integrity Input Prcess Output Input Cntrls Garbage-in Garbage-ut Frm Design All frms shuld be sequentially numbered Verify missing dcuments Use f turnarund dcuments Eliminate input errrs Input Cntrls Data Entry Checks Field check Characters prper type? Text, integer, date, and s n Sign check Prper arithmetic sign? Limit check Input checked against fixed value? Range check Input within lw and high range value? Size check Input fit within field? Cmpleteness check

2 Have all required data been entered? Validity check Input cmpared with master data t cnfirm existence Reasnableness check Lgical cmparisns Check digit verificatin Cmputed frm input value t catch typ errrs Prmpting Input requested by system Clse-lp verificatin Uses input data t retrieve and display related data Batch Input Cntrls Batch Prcessing Input multiple surce dcuments at nce in a grup Batch Ttals Cmpare input ttals t utput ttals Financial Sums a field that cntains mnetary values Hash Sums a nnfinancial numeric field Recrd cunt Sums a nnfinancial numeric field Prcessing Cntrls Data Matching Multiple data values must match befre prcessing ccurs.

3 File Labels Ensure crrect and mst current file is being updated. Batch Ttal Recalculatin Cmpare calculated batch ttal after prcessing t input ttals. Crss-Fting and Zer Balance Tests Cmpute ttals using multiple methds t ensure the same results. Write Prtectin Eliminate pssibility f verwriting r erasing existing data. Cncurrent Update Lcking recrds r fields when they are being updated s multiple users are nt updating at the same time. Output Cntrls User Review Verify reasnableness, cmpleteness, and ruted t intended individual Recnciliatin prcedures External data recnciliatin Data Transmissin Cntrls Check sums Hash f file transmitted, cmparisn made f hash befre and after transmissin Parity checking Bit added t each character transmitted, the characters can then be verified fr accuracy Cntrls Ensuring Availability Systems r infrmatin need t be available 24/7

4 It is nt pssible t ensure this s: Minimize Risks Preventive Maintenance Cleaning, prper strage Fault Tlerance Ability f a system t cntinue if a part fails Data Center Lcatin Minimize risk f natural and human created disasters. Training Less likely t make mistakes and will knw hw t recver, with minimal damage, frm errrs they d cmmit Patch Management Install, run, and keep current antivirus and anti-spyware prgrams Quick Recvery Back-up Incremental Cpy nly data that changed frm last partial back-up Differential Cpy nly data that changed frm last full back-up Business Cntinuity Plan (BCP) Hw t resume nt nly IT peratins, but all business prcesses Relcating t new ffices Hiring temprary replacements Change Cntrl Frmal prcess used t ensure that mdificatins t hardware, sftware, r prcesses d nt reduce systems reliability

5 Changes need t be dcumented. Changes need t be apprved by apprpriate manager. Changes need t be tested befre implementatins. All dcumentatin needs t be updated fr changes. Back-ut plans need t be adpted. User rights and privileges need t be mnitred during change. Disaster Recvery Plan (DRP) Prcedures t restre an rganizatin s IT functin in the event that its data center is destryed Cld Site An empty building that is prewired fr necessary telephne and Internet access, plus a cntract with ne r mre vendrs t prvide all necessary equipment within a specified perid f time Ht Site A facility that is nt nly prewired fr telephne and Internet access but als cntains all the cmputing and ffice equipment the rganizatin needs t perfrm its essential business activities Secnd Data-Center Used fr back-up and site mirrring